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1 | ------------------------------------------------------------------------------ |
2 | T H E /proc F I L E S Y S T E M | |
3 | ------------------------------------------------------------------------------ | |
4 | /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 | |
5 | Bodo Bauer <bb@ricochet.net> | |
6 | ||
7 | 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 | |
349888ee | 8 | move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 |
1da177e4 LT |
9 | ------------------------------------------------------------------------------ |
10 | Version 1.3 Kernel version 2.2.12 | |
11 | Kernel version 2.4.0-test11-pre4 | |
12 | ------------------------------------------------------------------------------ | |
349888ee | 13 | fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 |
1da177e4 LT |
14 | |
15 | Table of Contents | |
16 | ----------------- | |
17 | ||
18 | 0 Preface | |
19 | 0.1 Introduction/Credits | |
20 | 0.2 Legal Stuff | |
21 | ||
22 | 1 Collecting System Information | |
23 | 1.1 Process-Specific Subdirectories | |
24 | 1.2 Kernel data | |
25 | 1.3 IDE devices in /proc/ide | |
26 | 1.4 Networking info in /proc/net | |
27 | 1.5 SCSI info | |
28 | 1.6 Parallel port info in /proc/parport | |
29 | 1.7 TTY info in /proc/tty | |
30 | 1.8 Miscellaneous kernel statistics in /proc/stat | |
ae96b348 | 31 | 1.9 Ext4 file system parameters |
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32 | |
33 | 2 Modifying System Parameters | |
760df93e SF |
34 | |
35 | 3 Per-Process Parameters | |
fa0cbbf1 | 36 | 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer |
a63d83f4 | 37 | score |
760df93e SF |
38 | 3.2 /proc/<pid>/oom_score - Display current oom-killer score |
39 | 3.3 /proc/<pid>/io - Display the IO accounting fields | |
40 | 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings | |
41 | 3.5 /proc/<pid>/mountinfo - Information about mounts | |
4614a696 | 42 | 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm |
81841161 | 43 | 3.7 /proc/<pid>/task/<tid>/children - Information about task children |
f1d8c162 | 44 | 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file |
740a5ddb | 45 | 3.9 /proc/<pid>/map_files - Information about memory mapped files |
760df93e | 46 | |
0499680a VK |
47 | 4 Configuring procfs |
48 | 4.1 Mount options | |
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49 | |
50 | ------------------------------------------------------------------------------ | |
51 | Preface | |
52 | ------------------------------------------------------------------------------ | |
53 | ||
54 | 0.1 Introduction/Credits | |
55 | ------------------------ | |
56 | ||
57 | This documentation is part of a soon (or so we hope) to be released book on | |
58 | the SuSE Linux distribution. As there is no complete documentation for the | |
59 | /proc file system and we've used many freely available sources to write these | |
60 | chapters, it seems only fair to give the work back to the Linux community. | |
61 | This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm | |
62 | afraid it's still far from complete, but we hope it will be useful. As far as | |
63 | we know, it is the first 'all-in-one' document about the /proc file system. It | |
64 | is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, | |
65 | SPARC, AXP, etc., features, you probably won't find what you are looking for. | |
66 | It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But | |
67 | additions and patches are welcome and will be added to this document if you | |
68 | mail them to Bodo. | |
69 | ||
70 | We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of | |
71 | other people for help compiling this documentation. We'd also like to extend a | |
72 | special thank you to Andi Kleen for documentation, which we relied on heavily | |
73 | to create this document, as well as the additional information he provided. | |
74 | Thanks to everybody else who contributed source or docs to the Linux kernel | |
75 | and helped create a great piece of software... :) | |
76 | ||
77 | If you have any comments, corrections or additions, please don't hesitate to | |
78 | contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this | |
79 | document. | |
80 | ||
81 | The latest version of this document is available online at | |
0ea6e611 | 82 | http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html |
1da177e4 | 83 | |
0ea6e611 | 84 | If the above direction does not works for you, you could try the kernel |
1da177e4 LT |
85 | mailing list at linux-kernel@vger.kernel.org and/or try to reach me at |
86 | comandante@zaralinux.com. | |
87 | ||
88 | 0.2 Legal Stuff | |
89 | --------------- | |
90 | ||
91 | We don't guarantee the correctness of this document, and if you come to us | |
92 | complaining about how you screwed up your system because of incorrect | |
93 | documentation, we won't feel responsible... | |
94 | ||
95 | ------------------------------------------------------------------------------ | |
96 | CHAPTER 1: COLLECTING SYSTEM INFORMATION | |
97 | ------------------------------------------------------------------------------ | |
98 | ||
99 | ------------------------------------------------------------------------------ | |
100 | In This Chapter | |
101 | ------------------------------------------------------------------------------ | |
102 | * Investigating the properties of the pseudo file system /proc and its | |
103 | ability to provide information on the running Linux system | |
104 | * Examining /proc's structure | |
105 | * Uncovering various information about the kernel and the processes running | |
106 | on the system | |
107 | ------------------------------------------------------------------------------ | |
108 | ||
109 | ||
110 | The proc file system acts as an interface to internal data structures in the | |
111 | kernel. It can be used to obtain information about the system and to change | |
112 | certain kernel parameters at runtime (sysctl). | |
113 | ||
114 | First, we'll take a look at the read-only parts of /proc. In Chapter 2, we | |
115 | show you how you can use /proc/sys to change settings. | |
116 | ||
117 | 1.1 Process-Specific Subdirectories | |
118 | ----------------------------------- | |
119 | ||
120 | The directory /proc contains (among other things) one subdirectory for each | |
121 | process running on the system, which is named after the process ID (PID). | |
122 | ||
123 | The link self points to the process reading the file system. Each process | |
124 | subdirectory has the entries listed in Table 1-1. | |
125 | ||
126 | ||
349888ee | 127 | Table 1-1: Process specific entries in /proc |
1da177e4 | 128 | .............................................................................. |
b813e931 DR |
129 | File Content |
130 | clear_refs Clears page referenced bits shown in smaps output | |
131 | cmdline Command line arguments | |
132 | cpu Current and last cpu in which it was executed (2.4)(smp) | |
133 | cwd Link to the current working directory | |
134 | environ Values of environment variables | |
135 | exe Link to the executable of this process | |
136 | fd Directory, which contains all file descriptors | |
137 | maps Memory maps to executables and library files (2.4) | |
138 | mem Memory held by this process | |
139 | root Link to the root directory of this process | |
140 | stat Process status | |
141 | statm Process memory status information | |
142 | status Process status in human readable form | |
143 | wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan | |
03f890f8 | 144 | pagemap Page table |
2ec220e2 | 145 | stack Report full stack trace, enable via CONFIG_STACKTRACE |
349888ee | 146 | smaps a extension based on maps, showing the memory consumption of |
834f82e2 | 147 | each mapping and flags associated with it |
0c369711 RA |
148 | numa_maps an extension based on maps, showing the memory locality and |
149 | binding policy as well as mem usage (in pages) of each mapping. | |
1da177e4 LT |
150 | .............................................................................. |
151 | ||
152 | For example, to get the status information of a process, all you have to do is | |
153 | read the file /proc/PID/status: | |
154 | ||
349888ee SS |
155 | >cat /proc/self/status |
156 | Name: cat | |
157 | State: R (running) | |
158 | Tgid: 5452 | |
159 | Pid: 5452 | |
160 | PPid: 743 | |
1da177e4 | 161 | TracerPid: 0 (2.4) |
349888ee SS |
162 | Uid: 501 501 501 501 |
163 | Gid: 100 100 100 100 | |
164 | FDSize: 256 | |
165 | Groups: 100 14 16 | |
166 | VmPeak: 5004 kB | |
167 | VmSize: 5004 kB | |
168 | VmLck: 0 kB | |
169 | VmHWM: 476 kB | |
170 | VmRSS: 476 kB | |
171 | VmData: 156 kB | |
172 | VmStk: 88 kB | |
173 | VmExe: 68 kB | |
174 | VmLib: 1412 kB | |
175 | VmPTE: 20 kb | |
b084d435 | 176 | VmSwap: 0 kB |
349888ee SS |
177 | Threads: 1 |
178 | SigQ: 0/28578 | |
179 | SigPnd: 0000000000000000 | |
180 | ShdPnd: 0000000000000000 | |
181 | SigBlk: 0000000000000000 | |
182 | SigIgn: 0000000000000000 | |
183 | SigCgt: 0000000000000000 | |
184 | CapInh: 00000000fffffeff | |
185 | CapPrm: 0000000000000000 | |
186 | CapEff: 0000000000000000 | |
187 | CapBnd: ffffffffffffffff | |
2f4b3bf6 | 188 | Seccomp: 0 |
349888ee SS |
189 | voluntary_ctxt_switches: 0 |
190 | nonvoluntary_ctxt_switches: 1 | |
1da177e4 LT |
191 | |
192 | This shows you nearly the same information you would get if you viewed it with | |
193 | the ps command. In fact, ps uses the proc file system to obtain its | |
349888ee SS |
194 | information. But you get a more detailed view of the process by reading the |
195 | file /proc/PID/status. It fields are described in table 1-2. | |
196 | ||
197 | The statm file contains more detailed information about the process | |
198 | memory usage. Its seven fields are explained in Table 1-3. The stat file | |
199 | contains details information about the process itself. Its fields are | |
200 | explained in Table 1-4. | |
1da177e4 | 201 | |
34e55232 KH |
202 | (for SMP CONFIG users) |
203 | For making accounting scalable, RSS related information are handled in | |
204 | asynchronous manner and the vaule may not be very precise. To see a precise | |
205 | snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. | |
206 | It's slow but very precise. | |
207 | ||
cb2992a6 | 208 | Table 1-2: Contents of the status files (as of 2.6.30-rc7) |
349888ee SS |
209 | .............................................................................. |
210 | Field Content | |
211 | Name filename of the executable | |
212 | State state (R is running, S is sleeping, D is sleeping | |
213 | in an uninterruptible wait, Z is zombie, | |
214 | T is traced or stopped) | |
215 | Tgid thread group ID | |
216 | Pid process id | |
217 | PPid process id of the parent process | |
218 | TracerPid PID of process tracing this process (0 if not) | |
219 | Uid Real, effective, saved set, and file system UIDs | |
220 | Gid Real, effective, saved set, and file system GIDs | |
221 | FDSize number of file descriptor slots currently allocated | |
222 | Groups supplementary group list | |
223 | VmPeak peak virtual memory size | |
224 | VmSize total program size | |
225 | VmLck locked memory size | |
226 | VmHWM peak resident set size ("high water mark") | |
227 | VmRSS size of memory portions | |
228 | VmData size of data, stack, and text segments | |
229 | VmStk size of data, stack, and text segments | |
230 | VmExe size of text segment | |
231 | VmLib size of shared library code | |
232 | VmPTE size of page table entries | |
b084d435 | 233 | VmSwap size of swap usage (the number of referred swapents) |
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234 | Threads number of threads |
235 | SigQ number of signals queued/max. number for queue | |
236 | SigPnd bitmap of pending signals for the thread | |
237 | ShdPnd bitmap of shared pending signals for the process | |
238 | SigBlk bitmap of blocked signals | |
239 | SigIgn bitmap of ignored signals | |
c98be0c9 | 240 | SigCgt bitmap of caught signals |
349888ee SS |
241 | CapInh bitmap of inheritable capabilities |
242 | CapPrm bitmap of permitted capabilities | |
243 | CapEff bitmap of effective capabilities | |
244 | CapBnd bitmap of capabilities bounding set | |
2f4b3bf6 | 245 | Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) |
349888ee SS |
246 | Cpus_allowed mask of CPUs on which this process may run |
247 | Cpus_allowed_list Same as previous, but in "list format" | |
248 | Mems_allowed mask of memory nodes allowed to this process | |
249 | Mems_allowed_list Same as previous, but in "list format" | |
250 | voluntary_ctxt_switches number of voluntary context switches | |
251 | nonvoluntary_ctxt_switches number of non voluntary context switches | |
252 | .............................................................................. | |
1da177e4 | 253 | |
349888ee | 254 | Table 1-3: Contents of the statm files (as of 2.6.8-rc3) |
1da177e4 LT |
255 | .............................................................................. |
256 | Field Content | |
257 | size total program size (pages) (same as VmSize in status) | |
258 | resident size of memory portions (pages) (same as VmRSS in status) | |
259 | shared number of pages that are shared (i.e. backed by a file) | |
260 | trs number of pages that are 'code' (not including libs; broken, | |
261 | includes data segment) | |
262 | lrs number of pages of library (always 0 on 2.6) | |
263 | drs number of pages of data/stack (including libs; broken, | |
264 | includes library text) | |
265 | dt number of dirty pages (always 0 on 2.6) | |
266 | .............................................................................. | |
267 | ||
18d96779 | 268 | |
349888ee | 269 | Table 1-4: Contents of the stat files (as of 2.6.30-rc7) |
18d96779 KC |
270 | .............................................................................. |
271 | Field Content | |
272 | pid process id | |
273 | tcomm filename of the executable | |
274 | state state (R is running, S is sleeping, D is sleeping in an | |
275 | uninterruptible wait, Z is zombie, T is traced or stopped) | |
276 | ppid process id of the parent process | |
277 | pgrp pgrp of the process | |
278 | sid session id | |
279 | tty_nr tty the process uses | |
280 | tty_pgrp pgrp of the tty | |
281 | flags task flags | |
282 | min_flt number of minor faults | |
283 | cmin_flt number of minor faults with child's | |
284 | maj_flt number of major faults | |
285 | cmaj_flt number of major faults with child's | |
286 | utime user mode jiffies | |
287 | stime kernel mode jiffies | |
288 | cutime user mode jiffies with child's | |
289 | cstime kernel mode jiffies with child's | |
290 | priority priority level | |
291 | nice nice level | |
292 | num_threads number of threads | |
2e01e00e | 293 | it_real_value (obsolete, always 0) |
18d96779 KC |
294 | start_time time the process started after system boot |
295 | vsize virtual memory size | |
296 | rss resident set memory size | |
297 | rsslim current limit in bytes on the rss | |
298 | start_code address above which program text can run | |
299 | end_code address below which program text can run | |
b7643757 | 300 | start_stack address of the start of the main process stack |
18d96779 KC |
301 | esp current value of ESP |
302 | eip current value of EIP | |
349888ee SS |
303 | pending bitmap of pending signals |
304 | blocked bitmap of blocked signals | |
305 | sigign bitmap of ignored signals | |
c98be0c9 | 306 | sigcatch bitmap of caught signals |
18d96779 KC |
307 | wchan address where process went to sleep |
308 | 0 (place holder) | |
309 | 0 (place holder) | |
310 | exit_signal signal to send to parent thread on exit | |
311 | task_cpu which CPU the task is scheduled on | |
312 | rt_priority realtime priority | |
313 | policy scheduling policy (man sched_setscheduler) | |
314 | blkio_ticks time spent waiting for block IO | |
349888ee SS |
315 | gtime guest time of the task in jiffies |
316 | cgtime guest time of the task children in jiffies | |
b3f7f573 CG |
317 | start_data address above which program data+bss is placed |
318 | end_data address below which program data+bss is placed | |
319 | start_brk address above which program heap can be expanded with brk() | |
5b172087 CG |
320 | arg_start address above which program command line is placed |
321 | arg_end address below which program command line is placed | |
322 | env_start address above which program environment is placed | |
323 | env_end address below which program environment is placed | |
324 | exit_code the thread's exit_code in the form reported by the waitpid system call | |
18d96779 KC |
325 | .............................................................................. |
326 | ||
32e688b8 | 327 | The /proc/PID/maps file containing the currently mapped memory regions and |
349888ee SS |
328 | their access permissions. |
329 | ||
330 | The format is: | |
331 | ||
332 | address perms offset dev inode pathname | |
333 | ||
334 | 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test | |
335 | 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test | |
336 | 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] | |
337 | a7cb1000-a7cb2000 ---p 00000000 00:00 0 | |
34441427 | 338 | a7cb2000-a7eb2000 rw-p 00000000 00:00 0 |
349888ee | 339 | a7eb2000-a7eb3000 ---p 00000000 00:00 0 |
b7643757 | 340 | a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001] |
349888ee SS |
341 | a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 |
342 | a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 | |
343 | a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 | |
344 | a800b000-a800e000 rw-p 00000000 00:00 0 | |
345 | a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 | |
346 | a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 | |
347 | a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 | |
348 | a8024000-a8027000 rw-p 00000000 00:00 0 | |
349 | a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 | |
350 | a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 | |
351 | a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 | |
352 | aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] | |
353 | ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] | |
354 | ||
355 | where "address" is the address space in the process that it occupies, "perms" | |
356 | is a set of permissions: | |
357 | ||
358 | r = read | |
359 | w = write | |
360 | x = execute | |
361 | s = shared | |
362 | p = private (copy on write) | |
363 | ||
364 | "offset" is the offset into the mapping, "dev" is the device (major:minor), and | |
365 | "inode" is the inode on that device. 0 indicates that no inode is associated | |
366 | with the memory region, as the case would be with BSS (uninitialized data). | |
367 | The "pathname" shows the name associated file for this mapping. If the mapping | |
368 | is not associated with a file: | |
369 | ||
370 | [heap] = the heap of the program | |
371 | [stack] = the stack of the main process | |
b7643757 | 372 | [stack:1001] = the stack of the thread with tid 1001 |
349888ee SS |
373 | [vdso] = the "virtual dynamic shared object", |
374 | the kernel system call handler | |
375 | ||
376 | or if empty, the mapping is anonymous. | |
377 | ||
b7643757 SP |
378 | The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint |
379 | of the individual tasks of a process. In this file you will see a mapping marked | |
380 | as [stack] if that task sees it as a stack. This is a key difference from the | |
381 | content of /proc/PID/maps, where you will see all mappings that are being used | |
382 | as stack by all of those tasks. Hence, for the example above, the task-level | |
383 | map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this: | |
384 | ||
385 | 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test | |
386 | 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test | |
387 | 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] | |
388 | a7cb1000-a7cb2000 ---p 00000000 00:00 0 | |
389 | a7cb2000-a7eb2000 rw-p 00000000 00:00 0 | |
390 | a7eb2000-a7eb3000 ---p 00000000 00:00 0 | |
391 | a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack] | |
392 | a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 | |
393 | a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 | |
394 | a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 | |
395 | a800b000-a800e000 rw-p 00000000 00:00 0 | |
396 | a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 | |
397 | a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 | |
398 | a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 | |
399 | a8024000-a8027000 rw-p 00000000 00:00 0 | |
400 | a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 | |
401 | a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 | |
402 | a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 | |
403 | aff35000-aff4a000 rw-p 00000000 00:00 0 | |
404 | ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] | |
349888ee SS |
405 | |
406 | The /proc/PID/smaps is an extension based on maps, showing the memory | |
407 | consumption for each of the process's mappings. For each of mappings there | |
408 | is a series of lines such as the following: | |
409 | ||
410 | 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash | |
411 | Size: 1084 kB | |
412 | Rss: 892 kB | |
413 | Pss: 374 kB | |
414 | Shared_Clean: 892 kB | |
415 | Shared_Dirty: 0 kB | |
416 | Private_Clean: 0 kB | |
417 | Private_Dirty: 0 kB | |
418 | Referenced: 892 kB | |
b40d4f84 | 419 | Anonymous: 0 kB |
349888ee SS |
420 | Swap: 0 kB |
421 | KernelPageSize: 4 kB | |
422 | MMUPageSize: 4 kB | |
2d90508f | 423 | Locked: 374 kB |
834f82e2 | 424 | VmFlags: rd ex mr mw me de |
349888ee | 425 | |
834f82e2 | 426 | the first of these lines shows the same information as is displayed for the |
0f4d208f MM |
427 | mapping in /proc/PID/maps. The remaining lines show the size of the mapping |
428 | (size), the amount of the mapping that is currently resident in RAM (RSS), the | |
429 | process' proportional share of this mapping (PSS), the number of clean and | |
b40d4f84 NK |
430 | dirty private pages in the mapping. Note that even a page which is part of a |
431 | MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used | |
432 | by only one process, is accounted as private and not as shared. "Referenced" | |
433 | indicates the amount of memory currently marked as referenced or accessed. | |
434 | "Anonymous" shows the amount of memory that does not belong to any file. Even | |
435 | a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE | |
436 | and a page is modified, the file page is replaced by a private anonymous copy. | |
437 | "Swap" shows how much would-be-anonymous memory is also used, but out on | |
438 | swap. | |
349888ee | 439 | |
834f82e2 CG |
440 | "VmFlags" field deserves a separate description. This member represents the kernel |
441 | flags associated with the particular virtual memory area in two letter encoded | |
442 | manner. The codes are the following: | |
443 | rd - readable | |
444 | wr - writeable | |
445 | ex - executable | |
446 | sh - shared | |
447 | mr - may read | |
448 | mw - may write | |
449 | me - may execute | |
450 | ms - may share | |
451 | gd - stack segment growns down | |
452 | pf - pure PFN range | |
453 | dw - disabled write to the mapped file | |
454 | lo - pages are locked in memory | |
455 | io - memory mapped I/O area | |
456 | sr - sequential read advise provided | |
457 | rr - random read advise provided | |
458 | dc - do not copy area on fork | |
459 | de - do not expand area on remapping | |
460 | ac - area is accountable | |
461 | nr - swap space is not reserved for the area | |
462 | ht - area uses huge tlb pages | |
463 | nl - non-linear mapping | |
464 | ar - architecture specific flag | |
465 | dd - do not include area into core dump | |
ec8e41ae | 466 | sd - soft-dirty flag |
834f82e2 CG |
467 | mm - mixed map area |
468 | hg - huge page advise flag | |
469 | nh - no-huge page advise flag | |
470 | mg - mergable advise flag | |
471 | ||
472 | Note that there is no guarantee that every flag and associated mnemonic will | |
473 | be present in all further kernel releases. Things get changed, the flags may | |
474 | be vanished or the reverse -- new added. | |
475 | ||
349888ee SS |
476 | This file is only present if the CONFIG_MMU kernel configuration option is |
477 | enabled. | |
18d96779 | 478 | |
398499d5 | 479 | The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG |
0f8975ec PE |
480 | bits on both physical and virtual pages associated with a process, and the |
481 | soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details). | |
398499d5 MB |
482 | To clear the bits for all the pages associated with the process |
483 | > echo 1 > /proc/PID/clear_refs | |
484 | ||
485 | To clear the bits for the anonymous pages associated with the process | |
486 | > echo 2 > /proc/PID/clear_refs | |
487 | ||
488 | To clear the bits for the file mapped pages associated with the process | |
489 | > echo 3 > /proc/PID/clear_refs | |
0f8975ec PE |
490 | |
491 | To clear the soft-dirty bit | |
492 | > echo 4 > /proc/PID/clear_refs | |
493 | ||
695f0559 PC |
494 | To reset the peak resident set size ("high water mark") to the process's |
495 | current value: | |
496 | > echo 5 > /proc/PID/clear_refs | |
497 | ||
398499d5 MB |
498 | Any other value written to /proc/PID/clear_refs will have no effect. |
499 | ||
03f890f8 NK |
500 | The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags |
501 | using /proc/kpageflags and number of times a page is mapped using | |
502 | /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. | |
398499d5 | 503 | |
0c369711 RA |
504 | The /proc/pid/numa_maps is an extension based on maps, showing the memory |
505 | locality and binding policy, as well as the memory usage (in pages) of | |
506 | each mapping. The output follows a general format where mapping details get | |
507 | summarized separated by blank spaces, one mapping per each file line: | |
508 | ||
509 | address policy mapping details | |
510 | ||
198d1597 RA |
511 | 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 |
512 | 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 | |
513 | 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 | |
514 | 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 | |
515 | 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 | |
516 | 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 | |
517 | 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 | |
0c369711 | 518 | 320698b000 default file=/lib64/libc-2.12.so |
198d1597 RA |
519 | 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 |
520 | 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 | |
521 | 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 | |
522 | 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 | |
523 | 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 | |
524 | 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 | |
525 | 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 | |
526 | 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 | |
0c369711 RA |
527 | |
528 | Where: | |
529 | "address" is the starting address for the mapping; | |
530 | "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt); | |
531 | "mapping details" summarizes mapping data such as mapping type, page usage counters, | |
532 | node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page | |
533 | size, in KB, that is backing the mapping up. | |
534 | ||
1da177e4 LT |
535 | 1.2 Kernel data |
536 | --------------- | |
537 | ||
538 | Similar to the process entries, the kernel data files give information about | |
539 | the running kernel. The files used to obtain this information are contained in | |
349888ee | 540 | /proc and are listed in Table 1-5. Not all of these will be present in your |
1da177e4 LT |
541 | system. It depends on the kernel configuration and the loaded modules, which |
542 | files are there, and which are missing. | |
543 | ||
349888ee | 544 | Table 1-5: Kernel info in /proc |
1da177e4 LT |
545 | .............................................................................. |
546 | File Content | |
547 | apm Advanced power management info | |
548 | buddyinfo Kernel memory allocator information (see text) (2.5) | |
549 | bus Directory containing bus specific information | |
550 | cmdline Kernel command line | |
551 | cpuinfo Info about the CPU | |
552 | devices Available devices (block and character) | |
553 | dma Used DMS channels | |
554 | filesystems Supported filesystems | |
555 | driver Various drivers grouped here, currently rtc (2.4) | |
556 | execdomains Execdomains, related to security (2.4) | |
557 | fb Frame Buffer devices (2.4) | |
558 | fs File system parameters, currently nfs/exports (2.4) | |
559 | ide Directory containing info about the IDE subsystem | |
560 | interrupts Interrupt usage | |
561 | iomem Memory map (2.4) | |
562 | ioports I/O port usage | |
563 | irq Masks for irq to cpu affinity (2.4)(smp?) | |
564 | isapnp ISA PnP (Plug&Play) Info (2.4) | |
565 | kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) | |
566 | kmsg Kernel messages | |
567 | ksyms Kernel symbol table | |
568 | loadavg Load average of last 1, 5 & 15 minutes | |
569 | locks Kernel locks | |
570 | meminfo Memory info | |
571 | misc Miscellaneous | |
572 | modules List of loaded modules | |
573 | mounts Mounted filesystems | |
574 | net Networking info (see text) | |
a1b57ac0 | 575 | pagetypeinfo Additional page allocator information (see text) (2.5) |
1da177e4 | 576 | partitions Table of partitions known to the system |
8b60756a | 577 | pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, |
1da177e4 LT |
578 | decoupled by lspci (2.4) |
579 | rtc Real time clock | |
580 | scsi SCSI info (see text) | |
581 | slabinfo Slab pool info | |
d3d64df2 | 582 | softirqs softirq usage |
1da177e4 LT |
583 | stat Overall statistics |
584 | swaps Swap space utilization | |
585 | sys See chapter 2 | |
586 | sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) | |
587 | tty Info of tty drivers | |
49457896 | 588 | uptime Wall clock since boot, combined idle time of all cpus |
1da177e4 LT |
589 | version Kernel version |
590 | video bttv info of video resources (2.4) | |
a47a126a | 591 | vmallocinfo Show vmalloced areas |
1da177e4 LT |
592 | .............................................................................. |
593 | ||
594 | You can, for example, check which interrupts are currently in use and what | |
595 | they are used for by looking in the file /proc/interrupts: | |
596 | ||
597 | > cat /proc/interrupts | |
598 | CPU0 | |
599 | 0: 8728810 XT-PIC timer | |
600 | 1: 895 XT-PIC keyboard | |
601 | 2: 0 XT-PIC cascade | |
602 | 3: 531695 XT-PIC aha152x | |
603 | 4: 2014133 XT-PIC serial | |
604 | 5: 44401 XT-PIC pcnet_cs | |
605 | 8: 2 XT-PIC rtc | |
606 | 11: 8 XT-PIC i82365 | |
607 | 12: 182918 XT-PIC PS/2 Mouse | |
608 | 13: 1 XT-PIC fpu | |
609 | 14: 1232265 XT-PIC ide0 | |
610 | 15: 7 XT-PIC ide1 | |
611 | NMI: 0 | |
612 | ||
613 | In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the | |
614 | output of a SMP machine): | |
615 | ||
616 | > cat /proc/interrupts | |
617 | ||
618 | CPU0 CPU1 | |
619 | 0: 1243498 1214548 IO-APIC-edge timer | |
620 | 1: 8949 8958 IO-APIC-edge keyboard | |
621 | 2: 0 0 XT-PIC cascade | |
622 | 5: 11286 10161 IO-APIC-edge soundblaster | |
623 | 8: 1 0 IO-APIC-edge rtc | |
624 | 9: 27422 27407 IO-APIC-edge 3c503 | |
625 | 12: 113645 113873 IO-APIC-edge PS/2 Mouse | |
626 | 13: 0 0 XT-PIC fpu | |
627 | 14: 22491 24012 IO-APIC-edge ide0 | |
628 | 15: 2183 2415 IO-APIC-edge ide1 | |
629 | 17: 30564 30414 IO-APIC-level eth0 | |
630 | 18: 177 164 IO-APIC-level bttv | |
631 | NMI: 2457961 2457959 | |
632 | LOC: 2457882 2457881 | |
633 | ERR: 2155 | |
634 | ||
635 | NMI is incremented in this case because every timer interrupt generates a NMI | |
636 | (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. | |
637 | ||
638 | LOC is the local interrupt counter of the internal APIC of every CPU. | |
639 | ||
640 | ERR is incremented in the case of errors in the IO-APIC bus (the bus that | |
641 | connects the CPUs in a SMP system. This means that an error has been detected, | |
642 | the IO-APIC automatically retry the transmission, so it should not be a big | |
643 | problem, but you should read the SMP-FAQ. | |
644 | ||
38e760a1 JK |
645 | In 2.6.2* /proc/interrupts was expanded again. This time the goal was for |
646 | /proc/interrupts to display every IRQ vector in use by the system, not | |
647 | just those considered 'most important'. The new vectors are: | |
648 | ||
649 | THR -- interrupt raised when a machine check threshold counter | |
650 | (typically counting ECC corrected errors of memory or cache) exceeds | |
651 | a configurable threshold. Only available on some systems. | |
652 | ||
653 | TRM -- a thermal event interrupt occurs when a temperature threshold | |
654 | has been exceeded for the CPU. This interrupt may also be generated | |
655 | when the temperature drops back to normal. | |
656 | ||
657 | SPU -- a spurious interrupt is some interrupt that was raised then lowered | |
658 | by some IO device before it could be fully processed by the APIC. Hence | |
659 | the APIC sees the interrupt but does not know what device it came from. | |
660 | For this case the APIC will generate the interrupt with a IRQ vector | |
661 | of 0xff. This might also be generated by chipset bugs. | |
662 | ||
663 | RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are | |
664 | sent from one CPU to another per the needs of the OS. Typically, | |
665 | their statistics are used by kernel developers and interested users to | |
19f59460 | 666 | determine the occurrence of interrupts of the given type. |
38e760a1 | 667 | |
25985edc | 668 | The above IRQ vectors are displayed only when relevant. For example, |
38e760a1 JK |
669 | the threshold vector does not exist on x86_64 platforms. Others are |
670 | suppressed when the system is a uniprocessor. As of this writing, only | |
671 | i386 and x86_64 platforms support the new IRQ vector displays. | |
672 | ||
673 | Of some interest is the introduction of the /proc/irq directory to 2.4. | |
1da177e4 LT |
674 | It could be used to set IRQ to CPU affinity, this means that you can "hook" an |
675 | IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the | |
18404756 MK |
676 | irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and |
677 | prof_cpu_mask. | |
1da177e4 LT |
678 | |
679 | For example | |
680 | > ls /proc/irq/ | |
681 | 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask | |
18404756 | 682 | 1 11 13 15 17 19 3 5 7 9 default_smp_affinity |
1da177e4 LT |
683 | > ls /proc/irq/0/ |
684 | smp_affinity | |
685 | ||
18404756 MK |
686 | smp_affinity is a bitmask, in which you can specify which CPUs can handle the |
687 | IRQ, you can set it by doing: | |
1da177e4 | 688 | |
18404756 MK |
689 | > echo 1 > /proc/irq/10/smp_affinity |
690 | ||
691 | This means that only the first CPU will handle the IRQ, but you can also echo | |
692 | 5 which means that only the first and fourth CPU can handle the IRQ. | |
1da177e4 | 693 | |
18404756 MK |
694 | The contents of each smp_affinity file is the same by default: |
695 | ||
696 | > cat /proc/irq/0/smp_affinity | |
697 | ffffffff | |
1da177e4 | 698 | |
4b060420 MT |
699 | There is an alternate interface, smp_affinity_list which allows specifying |
700 | a cpu range instead of a bitmask: | |
701 | ||
702 | > cat /proc/irq/0/smp_affinity_list | |
703 | 1024-1031 | |
704 | ||
18404756 MK |
705 | The default_smp_affinity mask applies to all non-active IRQs, which are the |
706 | IRQs which have not yet been allocated/activated, and hence which lack a | |
707 | /proc/irq/[0-9]* directory. | |
1da177e4 | 708 | |
92d6b71a DS |
709 | The node file on an SMP system shows the node to which the device using the IRQ |
710 | reports itself as being attached. This hardware locality information does not | |
711 | include information about any possible driver locality preference. | |
712 | ||
18404756 | 713 | prof_cpu_mask specifies which CPUs are to be profiled by the system wide |
4b060420 | 714 | profiler. Default value is ffffffff (all cpus if there are only 32 of them). |
1da177e4 LT |
715 | |
716 | The way IRQs are routed is handled by the IO-APIC, and it's Round Robin | |
717 | between all the CPUs which are allowed to handle it. As usual the kernel has | |
718 | more info than you and does a better job than you, so the defaults are the | |
4b060420 MT |
719 | best choice for almost everyone. [Note this applies only to those IO-APIC's |
720 | that support "Round Robin" interrupt distribution.] | |
1da177e4 LT |
721 | |
722 | There are three more important subdirectories in /proc: net, scsi, and sys. | |
723 | The general rule is that the contents, or even the existence of these | |
724 | directories, depend on your kernel configuration. If SCSI is not enabled, the | |
725 | directory scsi may not exist. The same is true with the net, which is there | |
726 | only when networking support is present in the running kernel. | |
727 | ||
728 | The slabinfo file gives information about memory usage at the slab level. | |
729 | Linux uses slab pools for memory management above page level in version 2.2. | |
730 | Commonly used objects have their own slab pool (such as network buffers, | |
731 | directory cache, and so on). | |
732 | ||
733 | .............................................................................. | |
734 | ||
735 | > cat /proc/buddyinfo | |
736 | ||
737 | Node 0, zone DMA 0 4 5 4 4 3 ... | |
738 | Node 0, zone Normal 1 0 0 1 101 8 ... | |
739 | Node 0, zone HighMem 2 0 0 1 1 0 ... | |
740 | ||
a1b57ac0 | 741 | External fragmentation is a problem under some workloads, and buddyinfo is a |
1da177e4 LT |
742 | useful tool for helping diagnose these problems. Buddyinfo will give you a |
743 | clue as to how big an area you can safely allocate, or why a previous | |
744 | allocation failed. | |
745 | ||
746 | Each column represents the number of pages of a certain order which are | |
747 | available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in | |
748 | ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE | |
749 | available in ZONE_NORMAL, etc... | |
750 | ||
a1b57ac0 MG |
751 | More information relevant to external fragmentation can be found in |
752 | pagetypeinfo. | |
753 | ||
754 | > cat /proc/pagetypeinfo | |
755 | Page block order: 9 | |
756 | Pages per block: 512 | |
757 | ||
758 | Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 | |
759 | Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 | |
760 | Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 | |
761 | Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 | |
762 | Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 | |
763 | Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 | |
764 | Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 | |
765 | Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 | |
766 | Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 | |
767 | Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 | |
768 | Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 | |
769 | ||
770 | Number of blocks type Unmovable Reclaimable Movable Reserve Isolate | |
771 | Node 0, zone DMA 2 0 5 1 0 | |
772 | Node 0, zone DMA32 41 6 967 2 0 | |
773 | ||
774 | Fragmentation avoidance in the kernel works by grouping pages of different | |
775 | migrate types into the same contiguous regions of memory called page blocks. | |
776 | A page block is typically the size of the default hugepage size e.g. 2MB on | |
777 | X86-64. By keeping pages grouped based on their ability to move, the kernel | |
778 | can reclaim pages within a page block to satisfy a high-order allocation. | |
779 | ||
780 | The pagetypinfo begins with information on the size of a page block. It | |
781 | then gives the same type of information as buddyinfo except broken down | |
782 | by migrate-type and finishes with details on how many page blocks of each | |
783 | type exist. | |
784 | ||
785 | If min_free_kbytes has been tuned correctly (recommendations made by hugeadm | |
786 | from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can | |
787 | make an estimate of the likely number of huge pages that can be allocated | |
788 | at a given point in time. All the "Movable" blocks should be allocatable | |
789 | unless memory has been mlock()'d. Some of the Reclaimable blocks should | |
790 | also be allocatable although a lot of filesystem metadata may have to be | |
791 | reclaimed to achieve this. | |
792 | ||
1da177e4 LT |
793 | .............................................................................. |
794 | ||
795 | meminfo: | |
796 | ||
797 | Provides information about distribution and utilization of memory. This | |
798 | varies by architecture and compile options. The following is from a | |
799 | 16GB PIII, which has highmem enabled. You may not have all of these fields. | |
800 | ||
801 | > cat /proc/meminfo | |
802 | ||
2d90508f NK |
803 | The "Locked" indicates whether the mapping is locked in memory or not. |
804 | ||
1da177e4 LT |
805 | |
806 | MemTotal: 16344972 kB | |
807 | MemFree: 13634064 kB | |
34e431b0 | 808 | MemAvailable: 14836172 kB |
1da177e4 LT |
809 | Buffers: 3656 kB |
810 | Cached: 1195708 kB | |
811 | SwapCached: 0 kB | |
812 | Active: 891636 kB | |
813 | Inactive: 1077224 kB | |
814 | HighTotal: 15597528 kB | |
815 | HighFree: 13629632 kB | |
816 | LowTotal: 747444 kB | |
817 | LowFree: 4432 kB | |
818 | SwapTotal: 0 kB | |
819 | SwapFree: 0 kB | |
820 | Dirty: 968 kB | |
821 | Writeback: 0 kB | |
b88473f7 | 822 | AnonPages: 861800 kB |
1da177e4 | 823 | Mapped: 280372 kB |
b88473f7 MS |
824 | Slab: 284364 kB |
825 | SReclaimable: 159856 kB | |
826 | SUnreclaim: 124508 kB | |
827 | PageTables: 24448 kB | |
828 | NFS_Unstable: 0 kB | |
829 | Bounce: 0 kB | |
830 | WritebackTmp: 0 kB | |
1da177e4 LT |
831 | CommitLimit: 7669796 kB |
832 | Committed_AS: 100056 kB | |
1da177e4 LT |
833 | VmallocTotal: 112216 kB |
834 | VmallocUsed: 428 kB | |
835 | VmallocChunk: 111088 kB | |
69256994 | 836 | AnonHugePages: 49152 kB |
1da177e4 LT |
837 | |
838 | MemTotal: Total usable ram (i.e. physical ram minus a few reserved | |
839 | bits and the kernel binary code) | |
840 | MemFree: The sum of LowFree+HighFree | |
34e431b0 RR |
841 | MemAvailable: An estimate of how much memory is available for starting new |
842 | applications, without swapping. Calculated from MemFree, | |
843 | SReclaimable, the size of the file LRU lists, and the low | |
844 | watermarks in each zone. | |
845 | The estimate takes into account that the system needs some | |
846 | page cache to function well, and that not all reclaimable | |
847 | slab will be reclaimable, due to items being in use. The | |
848 | impact of those factors will vary from system to system. | |
1da177e4 LT |
849 | Buffers: Relatively temporary storage for raw disk blocks |
850 | shouldn't get tremendously large (20MB or so) | |
851 | Cached: in-memory cache for files read from the disk (the | |
852 | pagecache). Doesn't include SwapCached | |
853 | SwapCached: Memory that once was swapped out, is swapped back in but | |
854 | still also is in the swapfile (if memory is needed it | |
855 | doesn't need to be swapped out AGAIN because it is already | |
856 | in the swapfile. This saves I/O) | |
857 | Active: Memory that has been used more recently and usually not | |
858 | reclaimed unless absolutely necessary. | |
859 | Inactive: Memory which has been less recently used. It is more | |
860 | eligible to be reclaimed for other purposes | |
861 | HighTotal: | |
862 | HighFree: Highmem is all memory above ~860MB of physical memory | |
863 | Highmem areas are for use by userspace programs, or | |
864 | for the pagecache. The kernel must use tricks to access | |
865 | this memory, making it slower to access than lowmem. | |
866 | LowTotal: | |
867 | LowFree: Lowmem is memory which can be used for everything that | |
3f6dee9b | 868 | highmem can be used for, but it is also available for the |
1da177e4 LT |
869 | kernel's use for its own data structures. Among many |
870 | other things, it is where everything from the Slab is | |
871 | allocated. Bad things happen when you're out of lowmem. | |
872 | SwapTotal: total amount of swap space available | |
873 | SwapFree: Memory which has been evicted from RAM, and is temporarily | |
874 | on the disk | |
875 | Dirty: Memory which is waiting to get written back to the disk | |
876 | Writeback: Memory which is actively being written back to the disk | |
b88473f7 | 877 | AnonPages: Non-file backed pages mapped into userspace page tables |
69256994 | 878 | AnonHugePages: Non-file backed huge pages mapped into userspace page tables |
1da177e4 | 879 | Mapped: files which have been mmaped, such as libraries |
e82443c0 | 880 | Slab: in-kernel data structures cache |
b88473f7 MS |
881 | SReclaimable: Part of Slab, that might be reclaimed, such as caches |
882 | SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure | |
883 | PageTables: amount of memory dedicated to the lowest level of page | |
884 | tables. | |
885 | NFS_Unstable: NFS pages sent to the server, but not yet committed to stable | |
886 | storage | |
887 | Bounce: Memory used for block device "bounce buffers" | |
888 | WritebackTmp: Memory used by FUSE for temporary writeback buffers | |
1da177e4 LT |
889 | CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), |
890 | this is the total amount of memory currently available to | |
891 | be allocated on the system. This limit is only adhered to | |
892 | if strict overcommit accounting is enabled (mode 2 in | |
893 | 'vm.overcommit_memory'). | |
894 | The CommitLimit is calculated with the following formula: | |
7a9e6da1 PO |
895 | CommitLimit = ([total RAM pages] - [total huge TLB pages]) * |
896 | overcommit_ratio / 100 + [total swap pages] | |
1da177e4 LT |
897 | For example, on a system with 1G of physical RAM and 7G |
898 | of swap with a `vm.overcommit_ratio` of 30 it would | |
899 | yield a CommitLimit of 7.3G. | |
900 | For more details, see the memory overcommit documentation | |
901 | in vm/overcommit-accounting. | |
902 | Committed_AS: The amount of memory presently allocated on the system. | |
903 | The committed memory is a sum of all of the memory which | |
904 | has been allocated by processes, even if it has not been | |
905 | "used" by them as of yet. A process which malloc()'s 1G | |
46496022 MJ |
906 | of memory, but only touches 300M of it will show up as |
907 | using 1G. This 1G is memory which has been "committed" to | |
908 | by the VM and can be used at any time by the allocating | |
909 | application. With strict overcommit enabled on the system | |
910 | (mode 2 in 'vm.overcommit_memory'),allocations which would | |
911 | exceed the CommitLimit (detailed above) will not be permitted. | |
912 | This is useful if one needs to guarantee that processes will | |
913 | not fail due to lack of memory once that memory has been | |
914 | successfully allocated. | |
1da177e4 LT |
915 | VmallocTotal: total size of vmalloc memory area |
916 | VmallocUsed: amount of vmalloc area which is used | |
19f59460 | 917 | VmallocChunk: largest contiguous block of vmalloc area which is free |
1da177e4 | 918 | |
a47a126a ED |
919 | .............................................................................. |
920 | ||
921 | vmallocinfo: | |
922 | ||
923 | Provides information about vmalloced/vmaped areas. One line per area, | |
924 | containing the virtual address range of the area, size in bytes, | |
925 | caller information of the creator, and optional information depending | |
926 | on the kind of area : | |
927 | ||
928 | pages=nr number of pages | |
929 | phys=addr if a physical address was specified | |
930 | ioremap I/O mapping (ioremap() and friends) | |
931 | vmalloc vmalloc() area | |
932 | vmap vmap()ed pages | |
933 | user VM_USERMAP area | |
934 | vpages buffer for pages pointers was vmalloced (huge area) | |
935 | N<node>=nr (Only on NUMA kernels) | |
936 | Number of pages allocated on memory node <node> | |
937 | ||
938 | > cat /proc/vmallocinfo | |
939 | 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... | |
940 | /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 | |
941 | 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... | |
942 | /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 | |
943 | 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... | |
944 | phys=7fee8000 ioremap | |
945 | 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... | |
946 | phys=7fee7000 ioremap | |
947 | 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 | |
948 | 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... | |
949 | /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 | |
950 | 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... | |
951 | pages=2 vmalloc N1=2 | |
952 | 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... | |
953 | /0x130 [x_tables] pages=4 vmalloc N0=4 | |
954 | 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... | |
955 | pages=14 vmalloc N2=14 | |
956 | 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... | |
957 | pages=4 vmalloc N1=4 | |
958 | 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... | |
959 | pages=2 vmalloc N1=2 | |
960 | 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... | |
961 | pages=10 vmalloc N0=10 | |
1da177e4 | 962 | |
d3d64df2 KK |
963 | .............................................................................. |
964 | ||
965 | softirqs: | |
966 | ||
967 | Provides counts of softirq handlers serviced since boot time, for each cpu. | |
968 | ||
969 | > cat /proc/softirqs | |
970 | CPU0 CPU1 CPU2 CPU3 | |
971 | HI: 0 0 0 0 | |
972 | TIMER: 27166 27120 27097 27034 | |
973 | NET_TX: 0 0 0 17 | |
974 | NET_RX: 42 0 0 39 | |
975 | BLOCK: 0 0 107 1121 | |
976 | TASKLET: 0 0 0 290 | |
977 | SCHED: 27035 26983 26971 26746 | |
978 | HRTIMER: 0 0 0 0 | |
09223371 | 979 | RCU: 1678 1769 2178 2250 |
d3d64df2 KK |
980 | |
981 | ||
1da177e4 LT |
982 | 1.3 IDE devices in /proc/ide |
983 | ---------------------------- | |
984 | ||
985 | The subdirectory /proc/ide contains information about all IDE devices of which | |
986 | the kernel is aware. There is one subdirectory for each IDE controller, the | |
987 | file drivers and a link for each IDE device, pointing to the device directory | |
988 | in the controller specific subtree. | |
989 | ||
990 | The file drivers contains general information about the drivers used for the | |
991 | IDE devices: | |
992 | ||
993 | > cat /proc/ide/drivers | |
994 | ide-cdrom version 4.53 | |
995 | ide-disk version 1.08 | |
996 | ||
997 | More detailed information can be found in the controller specific | |
998 | subdirectories. These are named ide0, ide1 and so on. Each of these | |
349888ee | 999 | directories contains the files shown in table 1-6. |
1da177e4 LT |
1000 | |
1001 | ||
349888ee | 1002 | Table 1-6: IDE controller info in /proc/ide/ide? |
1da177e4 LT |
1003 | .............................................................................. |
1004 | File Content | |
1005 | channel IDE channel (0 or 1) | |
1006 | config Configuration (only for PCI/IDE bridge) | |
1007 | mate Mate name | |
1008 | model Type/Chipset of IDE controller | |
1009 | .............................................................................. | |
1010 | ||
1011 | Each device connected to a controller has a separate subdirectory in the | |
349888ee | 1012 | controllers directory. The files listed in table 1-7 are contained in these |
1da177e4 LT |
1013 | directories. |
1014 | ||
1015 | ||
349888ee | 1016 | Table 1-7: IDE device information |
1da177e4 LT |
1017 | .............................................................................. |
1018 | File Content | |
1019 | cache The cache | |
1020 | capacity Capacity of the medium (in 512Byte blocks) | |
1021 | driver driver and version | |
1022 | geometry physical and logical geometry | |
1023 | identify device identify block | |
1024 | media media type | |
1025 | model device identifier | |
1026 | settings device setup | |
1027 | smart_thresholds IDE disk management thresholds | |
1028 | smart_values IDE disk management values | |
1029 | .............................................................................. | |
1030 | ||
1031 | The most interesting file is settings. This file contains a nice overview of | |
1032 | the drive parameters: | |
1033 | ||
1034 | # cat /proc/ide/ide0/hda/settings | |
1035 | name value min max mode | |
1036 | ---- ----- --- --- ---- | |
1037 | bios_cyl 526 0 65535 rw | |
1038 | bios_head 255 0 255 rw | |
1039 | bios_sect 63 0 63 rw | |
1040 | breada_readahead 4 0 127 rw | |
1041 | bswap 0 0 1 r | |
1042 | file_readahead 72 0 2097151 rw | |
1043 | io_32bit 0 0 3 rw | |
1044 | keepsettings 0 0 1 rw | |
1045 | max_kb_per_request 122 1 127 rw | |
1046 | multcount 0 0 8 rw | |
1047 | nice1 1 0 1 rw | |
1048 | nowerr 0 0 1 rw | |
1049 | pio_mode write-only 0 255 w | |
1050 | slow 0 0 1 rw | |
1051 | unmaskirq 0 0 1 rw | |
1052 | using_dma 0 0 1 rw | |
1053 | ||
1054 | ||
1055 | 1.4 Networking info in /proc/net | |
1056 | -------------------------------- | |
1057 | ||
349888ee | 1058 | The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the |
1da177e4 | 1059 | additional values you get for IP version 6 if you configure the kernel to |
349888ee | 1060 | support this. Table 1-9 lists the files and their meaning. |
1da177e4 LT |
1061 | |
1062 | ||
349888ee | 1063 | Table 1-8: IPv6 info in /proc/net |
1da177e4 LT |
1064 | .............................................................................. |
1065 | File Content | |
1066 | udp6 UDP sockets (IPv6) | |
1067 | tcp6 TCP sockets (IPv6) | |
1068 | raw6 Raw device statistics (IPv6) | |
1069 | igmp6 IP multicast addresses, which this host joined (IPv6) | |
1070 | if_inet6 List of IPv6 interface addresses | |
1071 | ipv6_route Kernel routing table for IPv6 | |
1072 | rt6_stats Global IPv6 routing tables statistics | |
1073 | sockstat6 Socket statistics (IPv6) | |
1074 | snmp6 Snmp data (IPv6) | |
1075 | .............................................................................. | |
1076 | ||
1077 | ||
349888ee | 1078 | Table 1-9: Network info in /proc/net |
1da177e4 LT |
1079 | .............................................................................. |
1080 | File Content | |
1081 | arp Kernel ARP table | |
1082 | dev network devices with statistics | |
1083 | dev_mcast the Layer2 multicast groups a device is listening too | |
1084 | (interface index, label, number of references, number of bound | |
1085 | addresses). | |
1086 | dev_stat network device status | |
1087 | ip_fwchains Firewall chain linkage | |
1088 | ip_fwnames Firewall chain names | |
1089 | ip_masq Directory containing the masquerading tables | |
1090 | ip_masquerade Major masquerading table | |
1091 | netstat Network statistics | |
1092 | raw raw device statistics | |
1093 | route Kernel routing table | |
1094 | rpc Directory containing rpc info | |
1095 | rt_cache Routing cache | |
1096 | snmp SNMP data | |
1097 | sockstat Socket statistics | |
1098 | tcp TCP sockets | |
1da177e4 LT |
1099 | udp UDP sockets |
1100 | unix UNIX domain sockets | |
1101 | wireless Wireless interface data (Wavelan etc) | |
1102 | igmp IP multicast addresses, which this host joined | |
1103 | psched Global packet scheduler parameters. | |
1104 | netlink List of PF_NETLINK sockets | |
1105 | ip_mr_vifs List of multicast virtual interfaces | |
1106 | ip_mr_cache List of multicast routing cache | |
1107 | .............................................................................. | |
1108 | ||
1109 | You can use this information to see which network devices are available in | |
1110 | your system and how much traffic was routed over those devices: | |
1111 | ||
1112 | > cat /proc/net/dev | |
1113 | Inter-|Receive |[... | |
1114 | face |bytes packets errs drop fifo frame compressed multicast|[... | |
1115 | lo: 908188 5596 0 0 0 0 0 0 [... | |
1116 | ppp0:15475140 20721 410 0 0 410 0 0 [... | |
1117 | eth0: 614530 7085 0 0 0 0 0 1 [... | |
1118 | ||
1119 | ...] Transmit | |
1120 | ...] bytes packets errs drop fifo colls carrier compressed | |
1121 | ...] 908188 5596 0 0 0 0 0 0 | |
1122 | ...] 1375103 17405 0 0 0 0 0 0 | |
1123 | ...] 1703981 5535 0 0 0 3 0 0 | |
1124 | ||
a33f3224 | 1125 | In addition, each Channel Bond interface has its own directory. For |
1da177e4 LT |
1126 | example, the bond0 device will have a directory called /proc/net/bond0/. |
1127 | It will contain information that is specific to that bond, such as the | |
1128 | current slaves of the bond, the link status of the slaves, and how | |
1129 | many times the slaves link has failed. | |
1130 | ||
1131 | 1.5 SCSI info | |
1132 | ------------- | |
1133 | ||
1134 | If you have a SCSI host adapter in your system, you'll find a subdirectory | |
1135 | named after the driver for this adapter in /proc/scsi. You'll also see a list | |
1136 | of all recognized SCSI devices in /proc/scsi: | |
1137 | ||
1138 | >cat /proc/scsi/scsi | |
1139 | Attached devices: | |
1140 | Host: scsi0 Channel: 00 Id: 00 Lun: 00 | |
1141 | Vendor: IBM Model: DGHS09U Rev: 03E0 | |
1142 | Type: Direct-Access ANSI SCSI revision: 03 | |
1143 | Host: scsi0 Channel: 00 Id: 06 Lun: 00 | |
1144 | Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 | |
1145 | Type: CD-ROM ANSI SCSI revision: 02 | |
1146 | ||
1147 | ||
1148 | The directory named after the driver has one file for each adapter found in | |
1149 | the system. These files contain information about the controller, including | |
1150 | the used IRQ and the IO address range. The amount of information shown is | |
1151 | dependent on the adapter you use. The example shows the output for an Adaptec | |
1152 | AHA-2940 SCSI adapter: | |
1153 | ||
1154 | > cat /proc/scsi/aic7xxx/0 | |
1155 | ||
1156 | Adaptec AIC7xxx driver version: 5.1.19/3.2.4 | |
1157 | Compile Options: | |
1158 | TCQ Enabled By Default : Disabled | |
1159 | AIC7XXX_PROC_STATS : Disabled | |
1160 | AIC7XXX_RESET_DELAY : 5 | |
1161 | Adapter Configuration: | |
1162 | SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter | |
1163 | Ultra Wide Controller | |
1164 | PCI MMAPed I/O Base: 0xeb001000 | |
1165 | Adapter SEEPROM Config: SEEPROM found and used. | |
1166 | Adaptec SCSI BIOS: Enabled | |
1167 | IRQ: 10 | |
1168 | SCBs: Active 0, Max Active 2, | |
1169 | Allocated 15, HW 16, Page 255 | |
1170 | Interrupts: 160328 | |
1171 | BIOS Control Word: 0x18b6 | |
1172 | Adapter Control Word: 0x005b | |
1173 | Extended Translation: Enabled | |
1174 | Disconnect Enable Flags: 0xffff | |
1175 | Ultra Enable Flags: 0x0001 | |
1176 | Tag Queue Enable Flags: 0x0000 | |
1177 | Ordered Queue Tag Flags: 0x0000 | |
1178 | Default Tag Queue Depth: 8 | |
1179 | Tagged Queue By Device array for aic7xxx host instance 0: | |
1180 | {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} | |
1181 | Actual queue depth per device for aic7xxx host instance 0: | |
1182 | {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} | |
1183 | Statistics: | |
1184 | (scsi0:0:0:0) | |
1185 | Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 | |
1186 | Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) | |
1187 | Total transfers 160151 (74577 reads and 85574 writes) | |
1188 | (scsi0:0:6:0) | |
1189 | Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 | |
1190 | Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) | |
1191 | Total transfers 0 (0 reads and 0 writes) | |
1192 | ||
1193 | ||
1194 | 1.6 Parallel port info in /proc/parport | |
1195 | --------------------------------------- | |
1196 | ||
1197 | The directory /proc/parport contains information about the parallel ports of | |
1198 | your system. It has one subdirectory for each port, named after the port | |
1199 | number (0,1,2,...). | |
1200 | ||
349888ee | 1201 | These directories contain the four files shown in Table 1-10. |
1da177e4 LT |
1202 | |
1203 | ||
349888ee | 1204 | Table 1-10: Files in /proc/parport |
1da177e4 LT |
1205 | .............................................................................. |
1206 | File Content | |
1207 | autoprobe Any IEEE-1284 device ID information that has been acquired. | |
1208 | devices list of the device drivers using that port. A + will appear by the | |
1209 | name of the device currently using the port (it might not appear | |
1210 | against any). | |
1211 | hardware Parallel port's base address, IRQ line and DMA channel. | |
1212 | irq IRQ that parport is using for that port. This is in a separate | |
1213 | file to allow you to alter it by writing a new value in (IRQ | |
1214 | number or none). | |
1215 | .............................................................................. | |
1216 | ||
1217 | 1.7 TTY info in /proc/tty | |
1218 | ------------------------- | |
1219 | ||
1220 | Information about the available and actually used tty's can be found in the | |
1221 | directory /proc/tty.You'll find entries for drivers and line disciplines in | |
349888ee | 1222 | this directory, as shown in Table 1-11. |
1da177e4 LT |
1223 | |
1224 | ||
349888ee | 1225 | Table 1-11: Files in /proc/tty |
1da177e4 LT |
1226 | .............................................................................. |
1227 | File Content | |
1228 | drivers list of drivers and their usage | |
1229 | ldiscs registered line disciplines | |
1230 | driver/serial usage statistic and status of single tty lines | |
1231 | .............................................................................. | |
1232 | ||
1233 | To see which tty's are currently in use, you can simply look into the file | |
1234 | /proc/tty/drivers: | |
1235 | ||
1236 | > cat /proc/tty/drivers | |
1237 | pty_slave /dev/pts 136 0-255 pty:slave | |
1238 | pty_master /dev/ptm 128 0-255 pty:master | |
1239 | pty_slave /dev/ttyp 3 0-255 pty:slave | |
1240 | pty_master /dev/pty 2 0-255 pty:master | |
1241 | serial /dev/cua 5 64-67 serial:callout | |
1242 | serial /dev/ttyS 4 64-67 serial | |
1243 | /dev/tty0 /dev/tty0 4 0 system:vtmaster | |
1244 | /dev/ptmx /dev/ptmx 5 2 system | |
1245 | /dev/console /dev/console 5 1 system:console | |
1246 | /dev/tty /dev/tty 5 0 system:/dev/tty | |
1247 | unknown /dev/tty 4 1-63 console | |
1248 | ||
1249 | ||
1250 | 1.8 Miscellaneous kernel statistics in /proc/stat | |
1251 | ------------------------------------------------- | |
1252 | ||
1253 | Various pieces of information about kernel activity are available in the | |
1254 | /proc/stat file. All of the numbers reported in this file are aggregates | |
1255 | since the system first booted. For a quick look, simply cat the file: | |
1256 | ||
1257 | > cat /proc/stat | |
c574358e ED |
1258 | cpu 2255 34 2290 22625563 6290 127 456 0 0 |
1259 | cpu0 1132 34 1441 11311718 3675 127 438 0 0 | |
1260 | cpu1 1123 0 849 11313845 2614 0 18 0 0 | |
1da177e4 LT |
1261 | intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] |
1262 | ctxt 1990473 | |
1263 | btime 1062191376 | |
1264 | processes 2915 | |
1265 | procs_running 1 | |
1266 | procs_blocked 0 | |
d3d64df2 | 1267 | softirq 183433 0 21755 12 39 1137 231 21459 2263 |
1da177e4 LT |
1268 | |
1269 | The very first "cpu" line aggregates the numbers in all of the other "cpuN" | |
1270 | lines. These numbers identify the amount of time the CPU has spent performing | |
1271 | different kinds of work. Time units are in USER_HZ (typically hundredths of a | |
1272 | second). The meanings of the columns are as follows, from left to right: | |
1273 | ||
1274 | - user: normal processes executing in user mode | |
1275 | - nice: niced processes executing in user mode | |
1276 | - system: processes executing in kernel mode | |
1277 | - idle: twiddling thumbs | |
1278 | - iowait: waiting for I/O to complete | |
1279 | - irq: servicing interrupts | |
1280 | - softirq: servicing softirqs | |
b68f2c3a | 1281 | - steal: involuntary wait |
ce0e7b28 RO |
1282 | - guest: running a normal guest |
1283 | - guest_nice: running a niced guest | |
1da177e4 LT |
1284 | |
1285 | The "intr" line gives counts of interrupts serviced since boot time, for each | |
1286 | of the possible system interrupts. The first column is the total of all | |
3568a1db JMM |
1287 | interrupts serviced including unnumbered architecture specific interrupts; |
1288 | each subsequent column is the total for that particular numbered interrupt. | |
1289 | Unnumbered interrupts are not shown, only summed into the total. | |
1da177e4 LT |
1290 | |
1291 | The "ctxt" line gives the total number of context switches across all CPUs. | |
1292 | ||
1293 | The "btime" line gives the time at which the system booted, in seconds since | |
1294 | the Unix epoch. | |
1295 | ||
1296 | The "processes" line gives the number of processes and threads created, which | |
1297 | includes (but is not limited to) those created by calls to the fork() and | |
1298 | clone() system calls. | |
1299 | ||
e3cc2226 LGE |
1300 | The "procs_running" line gives the total number of threads that are |
1301 | running or ready to run (i.e., the total number of runnable threads). | |
1da177e4 LT |
1302 | |
1303 | The "procs_blocked" line gives the number of processes currently blocked, | |
1304 | waiting for I/O to complete. | |
1305 | ||
d3d64df2 KK |
1306 | The "softirq" line gives counts of softirqs serviced since boot time, for each |
1307 | of the possible system softirqs. The first column is the total of all | |
1308 | softirqs serviced; each subsequent column is the total for that particular | |
1309 | softirq. | |
1310 | ||
37515fac | 1311 | |
c9de560d | 1312 | 1.9 Ext4 file system parameters |
690b0543 | 1313 | ------------------------------- |
37515fac TT |
1314 | |
1315 | Information about mounted ext4 file systems can be found in | |
1316 | /proc/fs/ext4. Each mounted filesystem will have a directory in | |
1317 | /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or | |
1318 | /proc/fs/ext4/dm-0). The files in each per-device directory are shown | |
349888ee | 1319 | in Table 1-12, below. |
37515fac | 1320 | |
349888ee | 1321 | Table 1-12: Files in /proc/fs/ext4/<devname> |
37515fac TT |
1322 | .............................................................................. |
1323 | File Content | |
1324 | mb_groups details of multiblock allocator buddy cache of free blocks | |
37515fac TT |
1325 | .............................................................................. |
1326 | ||
23308ba5 JS |
1327 | 2.0 /proc/consoles |
1328 | ------------------ | |
1329 | Shows registered system console lines. | |
1330 | ||
1331 | To see which character device lines are currently used for the system console | |
1332 | /dev/console, you may simply look into the file /proc/consoles: | |
1333 | ||
1334 | > cat /proc/consoles | |
1335 | tty0 -WU (ECp) 4:7 | |
1336 | ttyS0 -W- (Ep) 4:64 | |
1337 | ||
1338 | The columns are: | |
1339 | ||
1340 | device name of the device | |
1341 | operations R = can do read operations | |
1342 | W = can do write operations | |
1343 | U = can do unblank | |
1344 | flags E = it is enabled | |
25985edc | 1345 | C = it is preferred console |
23308ba5 JS |
1346 | B = it is primary boot console |
1347 | p = it is used for printk buffer | |
1348 | b = it is not a TTY but a Braille device | |
1349 | a = it is safe to use when cpu is offline | |
1350 | major:minor major and minor number of the device separated by a colon | |
1da177e4 LT |
1351 | |
1352 | ------------------------------------------------------------------------------ | |
1353 | Summary | |
1354 | ------------------------------------------------------------------------------ | |
1355 | The /proc file system serves information about the running system. It not only | |
1356 | allows access to process data but also allows you to request the kernel status | |
1357 | by reading files in the hierarchy. | |
1358 | ||
1359 | The directory structure of /proc reflects the types of information and makes | |
1360 | it easy, if not obvious, where to look for specific data. | |
1361 | ------------------------------------------------------------------------------ | |
1362 | ||
1363 | ------------------------------------------------------------------------------ | |
1364 | CHAPTER 2: MODIFYING SYSTEM PARAMETERS | |
1365 | ------------------------------------------------------------------------------ | |
1366 | ||
1367 | ------------------------------------------------------------------------------ | |
1368 | In This Chapter | |
1369 | ------------------------------------------------------------------------------ | |
1370 | * Modifying kernel parameters by writing into files found in /proc/sys | |
1371 | * Exploring the files which modify certain parameters | |
1372 | * Review of the /proc/sys file tree | |
1373 | ------------------------------------------------------------------------------ | |
1374 | ||
1375 | ||
1376 | A very interesting part of /proc is the directory /proc/sys. This is not only | |
1377 | a source of information, it also allows you to change parameters within the | |
1378 | kernel. Be very careful when attempting this. You can optimize your system, | |
1379 | but you can also cause it to crash. Never alter kernel parameters on a | |
1380 | production system. Set up a development machine and test to make sure that | |
1381 | everything works the way you want it to. You may have no alternative but to | |
1382 | reboot the machine once an error has been made. | |
1383 | ||
1384 | To change a value, simply echo the new value into the file. An example is | |
1385 | given below in the section on the file system data. You need to be root to do | |
1386 | this. You can create your own boot script to perform this every time your | |
1387 | system boots. | |
1388 | ||
1389 | The files in /proc/sys can be used to fine tune and monitor miscellaneous and | |
1390 | general things in the operation of the Linux kernel. Since some of the files | |
1391 | can inadvertently disrupt your system, it is advisable to read both | |
1392 | documentation and source before actually making adjustments. In any case, be | |
1393 | very careful when writing to any of these files. The entries in /proc may | |
1394 | change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt | |
1395 | review the kernel documentation in the directory /usr/src/linux/Documentation. | |
1396 | This chapter is heavily based on the documentation included in the pre 2.2 | |
1397 | kernels, and became part of it in version 2.2.1 of the Linux kernel. | |
1398 | ||
395cf969 | 1399 | Please see: Documentation/sysctl/ directory for descriptions of these |
db0fb184 | 1400 | entries. |
9d0243bc | 1401 | |
760df93e SF |
1402 | ------------------------------------------------------------------------------ |
1403 | Summary | |
1404 | ------------------------------------------------------------------------------ | |
1405 | Certain aspects of kernel behavior can be modified at runtime, without the | |
1406 | need to recompile the kernel, or even to reboot the system. The files in the | |
1407 | /proc/sys tree can not only be read, but also modified. You can use the echo | |
1408 | command to write value into these files, thereby changing the default settings | |
1409 | of the kernel. | |
1410 | ------------------------------------------------------------------------------ | |
9d0243bc | 1411 | |
760df93e SF |
1412 | ------------------------------------------------------------------------------ |
1413 | CHAPTER 3: PER-PROCESS PARAMETERS | |
1414 | ------------------------------------------------------------------------------ | |
1da177e4 | 1415 | |
fa0cbbf1 | 1416 | 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score |
a63d83f4 DR |
1417 | -------------------------------------------------------------------------------- |
1418 | ||
fa0cbbf1 | 1419 | These file can be used to adjust the badness heuristic used to select which |
a63d83f4 DR |
1420 | process gets killed in out of memory conditions. |
1421 | ||
1422 | The badness heuristic assigns a value to each candidate task ranging from 0 | |
1423 | (never kill) to 1000 (always kill) to determine which process is targeted. The | |
1424 | units are roughly a proportion along that range of allowed memory the process | |
1425 | may allocate from based on an estimation of its current memory and swap use. | |
1426 | For example, if a task is using all allowed memory, its badness score will be | |
1427 | 1000. If it is using half of its allowed memory, its score will be 500. | |
1428 | ||
778c14af DR |
1429 | There is an additional factor included in the badness score: the current memory |
1430 | and swap usage is discounted by 3% for root processes. | |
a63d83f4 DR |
1431 | |
1432 | The amount of "allowed" memory depends on the context in which the oom killer | |
1433 | was called. If it is due to the memory assigned to the allocating task's cpuset | |
1434 | being exhausted, the allowed memory represents the set of mems assigned to that | |
1435 | cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed | |
1436 | memory represents the set of mempolicy nodes. If it is due to a memory | |
1437 | limit (or swap limit) being reached, the allowed memory is that configured | |
1438 | limit. Finally, if it is due to the entire system being out of memory, the | |
1439 | allowed memory represents all allocatable resources. | |
1440 | ||
1441 | The value of /proc/<pid>/oom_score_adj is added to the badness score before it | |
1442 | is used to determine which task to kill. Acceptable values range from -1000 | |
1443 | (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to | |
1444 | polarize the preference for oom killing either by always preferring a certain | |
1445 | task or completely disabling it. The lowest possible value, -1000, is | |
1446 | equivalent to disabling oom killing entirely for that task since it will always | |
1447 | report a badness score of 0. | |
1448 | ||
1449 | Consequently, it is very simple for userspace to define the amount of memory to | |
1450 | consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for | |
1451 | example, is roughly equivalent to allowing the remainder of tasks sharing the | |
1452 | same system, cpuset, mempolicy, or memory controller resources to use at least | |
1453 | 50% more memory. A value of -500, on the other hand, would be roughly | |
1454 | equivalent to discounting 50% of the task's allowed memory from being considered | |
1455 | as scoring against the task. | |
1456 | ||
fa0cbbf1 DR |
1457 | For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also |
1458 | be used to tune the badness score. Its acceptable values range from -16 | |
1459 | (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 | |
1460 | (OOM_DISABLE) to disable oom killing entirely for that task. Its value is | |
1461 | scaled linearly with /proc/<pid>/oom_score_adj. | |
1462 | ||
dabb16f6 MSB |
1463 | The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last |
1464 | value set by a CAP_SYS_RESOURCE process. To reduce the value any lower | |
1465 | requires CAP_SYS_RESOURCE. | |
1466 | ||
a63d83f4 | 1467 | Caveat: when a parent task is selected, the oom killer will sacrifice any first |
25985edc | 1468 | generation children with separate address spaces instead, if possible. This |
a63d83f4 DR |
1469 | avoids servers and important system daemons from being killed and loses the |
1470 | minimal amount of work. | |
1471 | ||
9e9e3cbc | 1472 | |
760df93e | 1473 | 3.2 /proc/<pid>/oom_score - Display current oom-killer score |
d7ff0dbf JFM |
1474 | ------------------------------------------------------------- |
1475 | ||
d7ff0dbf | 1476 | This file can be used to check the current score used by the oom-killer is for |
fa0cbbf1 DR |
1477 | any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which |
1478 | process should be killed in an out-of-memory situation. | |
1479 | ||
f9c99463 | 1480 | |
760df93e | 1481 | 3.3 /proc/<pid>/io - Display the IO accounting fields |
f9c99463 RK |
1482 | ------------------------------------------------------- |
1483 | ||
1484 | This file contains IO statistics for each running process | |
1485 | ||
1486 | Example | |
1487 | ------- | |
1488 | ||
1489 | test:/tmp # dd if=/dev/zero of=/tmp/test.dat & | |
1490 | [1] 3828 | |
1491 | ||
1492 | test:/tmp # cat /proc/3828/io | |
1493 | rchar: 323934931 | |
1494 | wchar: 323929600 | |
1495 | syscr: 632687 | |
1496 | syscw: 632675 | |
1497 | read_bytes: 0 | |
1498 | write_bytes: 323932160 | |
1499 | cancelled_write_bytes: 0 | |
1500 | ||
1501 | ||
1502 | Description | |
1503 | ----------- | |
1504 | ||
1505 | rchar | |
1506 | ----- | |
1507 | ||
1508 | I/O counter: chars read | |
1509 | The number of bytes which this task has caused to be read from storage. This | |
1510 | is simply the sum of bytes which this process passed to read() and pread(). | |
1511 | It includes things like tty IO and it is unaffected by whether or not actual | |
1512 | physical disk IO was required (the read might have been satisfied from | |
1513 | pagecache) | |
1514 | ||
1515 | ||
1516 | wchar | |
1517 | ----- | |
1518 | ||
1519 | I/O counter: chars written | |
1520 | The number of bytes which this task has caused, or shall cause to be written | |
1521 | to disk. Similar caveats apply here as with rchar. | |
1522 | ||
1523 | ||
1524 | syscr | |
1525 | ----- | |
1526 | ||
1527 | I/O counter: read syscalls | |
1528 | Attempt to count the number of read I/O operations, i.e. syscalls like read() | |
1529 | and pread(). | |
1530 | ||
1531 | ||
1532 | syscw | |
1533 | ----- | |
1534 | ||
1535 | I/O counter: write syscalls | |
1536 | Attempt to count the number of write I/O operations, i.e. syscalls like | |
1537 | write() and pwrite(). | |
1538 | ||
1539 | ||
1540 | read_bytes | |
1541 | ---------- | |
1542 | ||
1543 | I/O counter: bytes read | |
1544 | Attempt to count the number of bytes which this process really did cause to | |
1545 | be fetched from the storage layer. Done at the submit_bio() level, so it is | |
1546 | accurate for block-backed filesystems. <please add status regarding NFS and | |
1547 | CIFS at a later time> | |
1548 | ||
1549 | ||
1550 | write_bytes | |
1551 | ----------- | |
1552 | ||
1553 | I/O counter: bytes written | |
1554 | Attempt to count the number of bytes which this process caused to be sent to | |
1555 | the storage layer. This is done at page-dirtying time. | |
1556 | ||
1557 | ||
1558 | cancelled_write_bytes | |
1559 | --------------------- | |
1560 | ||
1561 | The big inaccuracy here is truncate. If a process writes 1MB to a file and | |
1562 | then deletes the file, it will in fact perform no writeout. But it will have | |
1563 | been accounted as having caused 1MB of write. | |
1564 | In other words: The number of bytes which this process caused to not happen, | |
1565 | by truncating pagecache. A task can cause "negative" IO too. If this task | |
1566 | truncates some dirty pagecache, some IO which another task has been accounted | |
a33f3224 | 1567 | for (in its write_bytes) will not be happening. We _could_ just subtract that |
f9c99463 RK |
1568 | from the truncating task's write_bytes, but there is information loss in doing |
1569 | that. | |
1570 | ||
1571 | ||
1572 | Note | |
1573 | ---- | |
1574 | ||
1575 | At its current implementation state, this is a bit racy on 32-bit machines: if | |
1576 | process A reads process B's /proc/pid/io while process B is updating one of | |
1577 | those 64-bit counters, process A could see an intermediate result. | |
1578 | ||
1579 | ||
1580 | More information about this can be found within the taskstats documentation in | |
1581 | Documentation/accounting. | |
1582 | ||
760df93e | 1583 | 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings |
bb90110d KH |
1584 | --------------------------------------------------------------- |
1585 | When a process is dumped, all anonymous memory is written to a core file as | |
1586 | long as the size of the core file isn't limited. But sometimes we don't want | |
1587 | to dump some memory segments, for example, huge shared memory. Conversely, | |
1588 | sometimes we want to save file-backed memory segments into a core file, not | |
1589 | only the individual files. | |
1590 | ||
1591 | /proc/<pid>/coredump_filter allows you to customize which memory segments | |
1592 | will be dumped when the <pid> process is dumped. coredump_filter is a bitmask | |
1593 | of memory types. If a bit of the bitmask is set, memory segments of the | |
1594 | corresponding memory type are dumped, otherwise they are not dumped. | |
1595 | ||
e575f111 | 1596 | The following 7 memory types are supported: |
bb90110d KH |
1597 | - (bit 0) anonymous private memory |
1598 | - (bit 1) anonymous shared memory | |
1599 | - (bit 2) file-backed private memory | |
1600 | - (bit 3) file-backed shared memory | |
b261dfea HK |
1601 | - (bit 4) ELF header pages in file-backed private memory areas (it is |
1602 | effective only if the bit 2 is cleared) | |
e575f111 KM |
1603 | - (bit 5) hugetlb private memory |
1604 | - (bit 6) hugetlb shared memory | |
bb90110d KH |
1605 | |
1606 | Note that MMIO pages such as frame buffer are never dumped and vDSO pages | |
1607 | are always dumped regardless of the bitmask status. | |
1608 | ||
e575f111 KM |
1609 | Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only |
1610 | effected by bit 5-6. | |
1611 | ||
1612 | Default value of coredump_filter is 0x23; this means all anonymous memory | |
1613 | segments and hugetlb private memory are dumped. | |
bb90110d KH |
1614 | |
1615 | If you don't want to dump all shared memory segments attached to pid 1234, | |
e575f111 | 1616 | write 0x21 to the process's proc file. |
bb90110d | 1617 | |
e575f111 | 1618 | $ echo 0x21 > /proc/1234/coredump_filter |
bb90110d KH |
1619 | |
1620 | When a new process is created, the process inherits the bitmask status from its | |
1621 | parent. It is useful to set up coredump_filter before the program runs. | |
1622 | For example: | |
1623 | ||
1624 | $ echo 0x7 > /proc/self/coredump_filter | |
1625 | $ ./some_program | |
1626 | ||
760df93e | 1627 | 3.5 /proc/<pid>/mountinfo - Information about mounts |
2d4d4864 RP |
1628 | -------------------------------------------------------- |
1629 | ||
1630 | This file contains lines of the form: | |
1631 | ||
1632 | 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue | |
1633 | (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) | |
1634 | ||
1635 | (1) mount ID: unique identifier of the mount (may be reused after umount) | |
1636 | (2) parent ID: ID of parent (or of self for the top of the mount tree) | |
1637 | (3) major:minor: value of st_dev for files on filesystem | |
1638 | (4) root: root of the mount within the filesystem | |
1639 | (5) mount point: mount point relative to the process's root | |
1640 | (6) mount options: per mount options | |
1641 | (7) optional fields: zero or more fields of the form "tag[:value]" | |
1642 | (8) separator: marks the end of the optional fields | |
1643 | (9) filesystem type: name of filesystem of the form "type[.subtype]" | |
1644 | (10) mount source: filesystem specific information or "none" | |
1645 | (11) super options: per super block options | |
1646 | ||
1647 | Parsers should ignore all unrecognised optional fields. Currently the | |
1648 | possible optional fields are: | |
1649 | ||
1650 | shared:X mount is shared in peer group X | |
1651 | master:X mount is slave to peer group X | |
97e7e0f7 | 1652 | propagate_from:X mount is slave and receives propagation from peer group X (*) |
2d4d4864 RP |
1653 | unbindable mount is unbindable |
1654 | ||
97e7e0f7 MS |
1655 | (*) X is the closest dominant peer group under the process's root. If |
1656 | X is the immediate master of the mount, or if there's no dominant peer | |
1657 | group under the same root, then only the "master:X" field is present | |
1658 | and not the "propagate_from:X" field. | |
1659 | ||
2d4d4864 RP |
1660 | For more information on mount propagation see: |
1661 | ||
1662 | Documentation/filesystems/sharedsubtree.txt | |
1663 | ||
4614a696 | 1664 | |
1665 | 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm | |
1666 | -------------------------------------------------------- | |
1667 | These files provide a method to access a tasks comm value. It also allows for | |
1668 | a task to set its own or one of its thread siblings comm value. The comm value | |
1669 | is limited in size compared to the cmdline value, so writing anything longer | |
1670 | then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated | |
1671 | comm value. | |
0499680a VK |
1672 | |
1673 | ||
81841161 CG |
1674 | 3.7 /proc/<pid>/task/<tid>/children - Information about task children |
1675 | ------------------------------------------------------------------------- | |
1676 | This file provides a fast way to retrieve first level children pids | |
1677 | of a task pointed by <pid>/<tid> pair. The format is a space separated | |
1678 | stream of pids. | |
1679 | ||
1680 | Note the "first level" here -- if a child has own children they will | |
1681 | not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children | |
1682 | to obtain the descendants. | |
1683 | ||
1684 | Since this interface is intended to be fast and cheap it doesn't | |
1685 | guarantee to provide precise results and some children might be | |
1686 | skipped, especially if they've exited right after we printed their | |
1687 | pids, so one need to either stop or freeze processes being inspected | |
1688 | if precise results are needed. | |
1689 | ||
1690 | ||
49d063cb | 1691 | 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file |
f1d8c162 CG |
1692 | --------------------------------------------------------------- |
1693 | This file provides information associated with an opened file. The regular | |
49d063cb AV |
1694 | files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos' |
1695 | represents the current offset of the opened file in decimal form [see lseek(2) | |
1696 | for details], 'flags' denotes the octal O_xxx mask the file has been | |
1697 | created with [see open(2) for details] and 'mnt_id' represents mount ID of | |
1698 | the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo | |
1699 | for details]. | |
f1d8c162 CG |
1700 | |
1701 | A typical output is | |
1702 | ||
1703 | pos: 0 | |
1704 | flags: 0100002 | |
49d063cb | 1705 | mnt_id: 19 |
f1d8c162 CG |
1706 | |
1707 | The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags | |
1708 | pair provide additional information particular to the objects they represent. | |
1709 | ||
1710 | Eventfd files | |
1711 | ~~~~~~~~~~~~~ | |
1712 | pos: 0 | |
1713 | flags: 04002 | |
49d063cb | 1714 | mnt_id: 9 |
f1d8c162 CG |
1715 | eventfd-count: 5a |
1716 | ||
1717 | where 'eventfd-count' is hex value of a counter. | |
1718 | ||
1719 | Signalfd files | |
1720 | ~~~~~~~~~~~~~~ | |
1721 | pos: 0 | |
1722 | flags: 04002 | |
49d063cb | 1723 | mnt_id: 9 |
f1d8c162 CG |
1724 | sigmask: 0000000000000200 |
1725 | ||
1726 | where 'sigmask' is hex value of the signal mask associated | |
1727 | with a file. | |
1728 | ||
1729 | Epoll files | |
1730 | ~~~~~~~~~~~ | |
1731 | pos: 0 | |
1732 | flags: 02 | |
49d063cb | 1733 | mnt_id: 9 |
f1d8c162 CG |
1734 | tfd: 5 events: 1d data: ffffffffffffffff |
1735 | ||
1736 | where 'tfd' is a target file descriptor number in decimal form, | |
1737 | 'events' is events mask being watched and the 'data' is data | |
1738 | associated with a target [see epoll(7) for more details]. | |
1739 | ||
1740 | Fsnotify files | |
1741 | ~~~~~~~~~~~~~~ | |
1742 | For inotify files the format is the following | |
1743 | ||
1744 | pos: 0 | |
1745 | flags: 02000000 | |
1746 | inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d | |
1747 | ||
1748 | where 'wd' is a watch descriptor in decimal form, ie a target file | |
1749 | descriptor number, 'ino' and 'sdev' are inode and device where the | |
1750 | target file resides and the 'mask' is the mask of events, all in hex | |
1751 | form [see inotify(7) for more details]. | |
1752 | ||
1753 | If the kernel was built with exportfs support, the path to the target | |
1754 | file is encoded as a file handle. The file handle is provided by three | |
1755 | fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex | |
1756 | format. | |
1757 | ||
1758 | If the kernel is built without exportfs support the file handle won't be | |
1759 | printed out. | |
1760 | ||
e71ec593 | 1761 | If there is no inotify mark attached yet the 'inotify' line will be omitted. |
f1d8c162 | 1762 | |
e71ec593 | 1763 | For fanotify files the format is |
f1d8c162 CG |
1764 | |
1765 | pos: 0 | |
1766 | flags: 02 | |
49d063cb | 1767 | mnt_id: 9 |
e71ec593 CG |
1768 | fanotify flags:10 event-flags:0 |
1769 | fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 | |
1770 | fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 | |
1771 | ||
1772 | where fanotify 'flags' and 'event-flags' are values used in fanotify_init | |
1773 | call, 'mnt_id' is the mount point identifier, 'mflags' is the value of | |
1774 | flags associated with mark which are tracked separately from events | |
1775 | mask. 'ino', 'sdev' are target inode and device, 'mask' is the events | |
1776 | mask and 'ignored_mask' is the mask of events which are to be ignored. | |
1777 | All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' | |
1778 | does provide information about flags and mask used in fanotify_mark | |
1779 | call [see fsnotify manpage for details]. | |
1780 | ||
1781 | While the first three lines are mandatory and always printed, the rest is | |
1782 | optional and may be omitted if no marks created yet. | |
f1d8c162 | 1783 | |
854d06d9 CG |
1784 | Timerfd files |
1785 | ~~~~~~~~~~~~~ | |
1786 | ||
1787 | pos: 0 | |
1788 | flags: 02 | |
1789 | mnt_id: 9 | |
1790 | clockid: 0 | |
1791 | ticks: 0 | |
1792 | settime flags: 01 | |
1793 | it_value: (0, 49406829) | |
1794 | it_interval: (1, 0) | |
1795 | ||
1796 | where 'clockid' is the clock type and 'ticks' is the number of the timer expirations | |
1797 | that have occurred [see timerfd_create(2) for details]. 'settime flags' are | |
1798 | flags in octal form been used to setup the timer [see timerfd_settime(2) for | |
1799 | details]. 'it_value' is remaining time until the timer exiration. | |
1800 | 'it_interval' is the interval for the timer. Note the timer might be set up | |
1801 | with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' | |
1802 | still exhibits timer's remaining time. | |
f1d8c162 | 1803 | |
740a5ddb CG |
1804 | 3.9 /proc/<pid>/map_files - Information about memory mapped files |
1805 | --------------------------------------------------------------------- | |
1806 | This directory contains symbolic links which represent memory mapped files | |
1807 | the process is maintaining. Example output: | |
1808 | ||
1809 | | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so | |
1810 | | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so | |
1811 | | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so | |
1812 | | ... | |
1813 | | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 | |
1814 | | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls | |
1815 | ||
1816 | The name of a link represents the virtual memory bounds of a mapping, i.e. | |
1817 | vm_area_struct::vm_start-vm_area_struct::vm_end. | |
1818 | ||
1819 | The main purpose of the map_files is to retrieve a set of memory mapped | |
1820 | files in a fast way instead of parsing /proc/<pid>/maps or | |
1821 | /proc/<pid>/smaps, both of which contain many more records. At the same | |
1822 | time one can open(2) mappings from the listings of two processes and | |
1823 | comparing their inode numbers to figure out which anonymous memory areas | |
1824 | are actually shared. | |
1825 | ||
0499680a VK |
1826 | ------------------------------------------------------------------------------ |
1827 | Configuring procfs | |
1828 | ------------------------------------------------------------------------------ | |
1829 | ||
1830 | 4.1 Mount options | |
1831 | --------------------- | |
1832 | ||
1833 | The following mount options are supported: | |
1834 | ||
1835 | hidepid= Set /proc/<pid>/ access mode. | |
1836 | gid= Set the group authorized to learn processes information. | |
1837 | ||
1838 | hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories | |
1839 | (default). | |
1840 | ||
1841 | hidepid=1 means users may not access any /proc/<pid>/ directories but their | |
1842 | own. Sensitive files like cmdline, sched*, status are now protected against | |
1843 | other users. This makes it impossible to learn whether any user runs | |
1844 | specific program (given the program doesn't reveal itself by its behaviour). | |
1845 | As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, | |
1846 | poorly written programs passing sensitive information via program arguments are | |
1847 | now protected against local eavesdroppers. | |
1848 | ||
1849 | hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other | |
1850 | users. It doesn't mean that it hides a fact whether a process with a specific | |
1851 | pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), | |
1852 | but it hides process' uid and gid, which may be learned by stat()'ing | |
1853 | /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering | |
1854 | information about running processes, whether some daemon runs with elevated | |
1855 | privileges, whether other user runs some sensitive program, whether other users | |
1856 | run any program at all, etc. | |
1857 | ||
1858 | gid= defines a group authorized to learn processes information otherwise | |
1859 | prohibited by hidepid=. If you use some daemon like identd which needs to learn | |
1860 | information about processes information, just add identd to this group. |