Commit | Line | Data |
---|---|---|
c906108c SS |
1 | /* Caching code. Typically used by remote back ends for |
2 | caching remote memory. | |
3 | ||
917317f4 | 4 | Copyright 1992-1993, 1995, 1998-1999 Free Software Foundation, Inc. |
c906108c SS |
5 | |
6 | This file is part of GDB. | |
7 | ||
8 | This program is free software; you can redistribute it and/or modify | |
9 | it under the terms of the GNU General Public License as published by | |
10 | the Free Software Foundation; either version 2 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | This program is distributed in the hope that it will be useful, | |
14 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | GNU General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with this program; if not, write to the Free Software | |
c5aa993b JM |
20 | Foundation, Inc., 59 Temple Place - Suite 330, |
21 | Boston, MA 02111-1307, USA. */ | |
c906108c SS |
22 | |
23 | #include "defs.h" | |
24 | #include "dcache.h" | |
25 | #include "gdbcmd.h" | |
26 | #include "gdb_string.h" | |
27 | #include "gdbcore.h" | |
28 | ||
29 | /* | |
30 | The data cache could lead to incorrect results because it doesn't know | |
31 | about volatile variables, thus making it impossible to debug | |
32 | functions which use memory mapped I/O devices. | |
33 | ||
34 | set remotecache 0 | |
35 | ||
36 | In those cases. | |
37 | ||
38 | In general the dcache speeds up performance, some speed improvement | |
39 | comes from the actual caching mechanism, but the major gain is in | |
40 | the reduction of the remote protocol overhead; instead of reading | |
41 | or writing a large area of memory in 4 byte requests, the cache | |
42 | bundles up the requests into 32 byte (actually LINE_SIZE) chunks. | |
43 | Reducing the overhead to an eighth of what it was. This is very | |
44 | obvious when displaying a large amount of data, | |
45 | ||
46 | eg, x/200x 0 | |
47 | ||
48 | caching | no yes | |
49 | ---------------------------- | |
50 | first time | 4 sec 2 sec improvement due to chunking | |
51 | second time | 4 sec 0 sec improvement due to caching | |
52 | ||
53 | The cache structure is unusual, we keep a number of cache blocks | |
54 | (DCACHE_SIZE) and each one caches a LINE_SIZEed area of memory. | |
55 | Within each line we remember the address of the line (always a | |
56 | multiple of the LINE_SIZE) and a vector of bytes over the range. | |
57 | There's another vector which contains the state of the bytes. | |
58 | ||
59 | ENTRY_BAD means that the byte is just plain wrong, and has no | |
60 | correspondence with anything else (as it would when the cache is | |
61 | turned on, but nothing has been done to it. | |
62 | ||
63 | ENTRY_DIRTY means that the byte has some data in it which should be | |
64 | written out to the remote target one day, but contains correct | |
65 | data. ENTRY_OK means that the data is the same in the cache as it | |
66 | is in remote memory. | |
67 | ||
68 | ||
69 | The ENTRY_DIRTY state is necessary because GDB likes to write large | |
70 | lumps of memory in small bits. If the caching mechanism didn't | |
71 | maintain the DIRTY information, then something like a two byte | |
72 | write would mean that the entire cache line would have to be read, | |
73 | the two bytes modified and then written out again. The alternative | |
74 | would be to not read in the cache line in the first place, and just | |
75 | write the two bytes directly into target memory. The trouble with | |
76 | that is that it really nails performance, because of the remote | |
77 | protocol overhead. This way, all those little writes are bundled | |
78 | up into an entire cache line write in one go, without having to | |
79 | read the cache line in the first place. | |
80 | ||
81 | ||
c5aa993b | 82 | */ |
c906108c SS |
83 | |
84 | ||
85 | /* This value regulates the number of cache blocks stored. | |
86 | Smaller values reduce the time spent searching for a cache | |
87 | line, and reduce memory requirements, but increase the risk | |
88 | of a line not being in memory */ | |
89 | ||
c5aa993b | 90 | #define DCACHE_SIZE 64 |
c906108c SS |
91 | |
92 | /* This value regulates the size of a cache line. Smaller values | |
93 | reduce the time taken to read a single byte, but reduce overall | |
94 | throughput. */ | |
95 | ||
c5aa993b | 96 | #define LINE_SIZE_POWER (5) |
c906108c SS |
97 | #define LINE_SIZE (1 << LINE_SIZE_POWER) |
98 | ||
99 | /* Each cache block holds LINE_SIZE bytes of data | |
100 | starting at a multiple-of-LINE_SIZE address. */ | |
101 | ||
c5aa993b | 102 | #define LINE_SIZE_MASK ((LINE_SIZE - 1)) |
c906108c SS |
103 | #define XFORM(x) ((x) & LINE_SIZE_MASK) |
104 | #define MASK(x) ((x) & ~LINE_SIZE_MASK) | |
105 | ||
106 | ||
c5aa993b JM |
107 | #define ENTRY_BAD 0 /* data at this byte is wrong */ |
108 | #define ENTRY_DIRTY 1 /* data at this byte needs to be written back */ | |
109 | #define ENTRY_OK 2 /* data at this byte is same as in memory */ | |
c906108c SS |
110 | |
111 | ||
112 | struct dcache_block | |
c5aa993b JM |
113 | { |
114 | struct dcache_block *p; /* next in list */ | |
115 | CORE_ADDR addr; /* Address for which data is recorded. */ | |
116 | char data[LINE_SIZE]; /* bytes at given address */ | |
117 | unsigned char state[LINE_SIZE]; /* what state the data is in */ | |
c906108c | 118 | |
c5aa993b JM |
119 | /* whether anything in state is dirty - used to speed up the |
120 | dirty scan. */ | |
121 | int anydirty; | |
c906108c | 122 | |
c5aa993b JM |
123 | int refs; |
124 | }; | |
c906108c SS |
125 | |
126 | ||
c5aa993b JM |
127 | struct dcache_struct |
128 | { | |
129 | /* Function to actually read the target memory. */ | |
130 | memxferfunc read_memory; | |
c906108c | 131 | |
c5aa993b JM |
132 | /* Function to actually write the target memory */ |
133 | memxferfunc write_memory; | |
c906108c | 134 | |
c5aa993b JM |
135 | /* free list */ |
136 | struct dcache_block *free_head; | |
137 | struct dcache_block *free_tail; | |
c906108c | 138 | |
c5aa993b JM |
139 | /* in use list */ |
140 | struct dcache_block *valid_head; | |
141 | struct dcache_block *valid_tail; | |
c906108c | 142 | |
c5aa993b JM |
143 | /* The cache itself. */ |
144 | struct dcache_block *the_cache; | |
c906108c | 145 | |
c5aa993b JM |
146 | /* potentially, if the cache was enabled, and then turned off, and |
147 | then turned on again, the stuff in it could be stale, so this is | |
148 | used to mark it */ | |
149 | int cache_has_stuff; | |
150 | }; | |
c906108c | 151 | |
a14ed312 | 152 | static int dcache_poke_byte (DCACHE * dcache, CORE_ADDR addr, char *ptr); |
c906108c | 153 | |
a14ed312 | 154 | static int dcache_peek_byte (DCACHE * dcache, CORE_ADDR addr, char *ptr); |
c906108c | 155 | |
a14ed312 | 156 | static struct dcache_block *dcache_hit (DCACHE * dcache, CORE_ADDR addr); |
c906108c | 157 | |
a14ed312 | 158 | static int dcache_write_line (DCACHE * dcache, struct dcache_block *db); |
c906108c | 159 | |
a14ed312 | 160 | static struct dcache_block *dcache_alloc (DCACHE * dcache); |
c906108c | 161 | |
a14ed312 | 162 | static int dcache_writeback (DCACHE * dcache); |
c906108c | 163 | |
a14ed312 | 164 | static void dcache_info (char *exp, int tty); |
c906108c | 165 | |
a14ed312 | 166 | void _initialize_dcache (void); |
c906108c | 167 | |
917317f4 | 168 | static int dcache_enabled_p = 0; |
c906108c | 169 | |
c5aa993b | 170 | DCACHE *last_cache; /* Used by info dcache */ |
c906108c SS |
171 | |
172 | ||
173 | /* Free all the data cache blocks, thus discarding all cached data. */ | |
174 | ||
175 | void | |
fba45db2 | 176 | dcache_flush (DCACHE *dcache) |
c906108c SS |
177 | { |
178 | int i; | |
179 | dcache->valid_head = 0; | |
180 | dcache->valid_tail = 0; | |
181 | ||
182 | dcache->free_head = 0; | |
183 | dcache->free_tail = 0; | |
184 | ||
185 | for (i = 0; i < DCACHE_SIZE; i++) | |
186 | { | |
187 | struct dcache_block *db = dcache->the_cache + i; | |
188 | ||
189 | if (!dcache->free_head) | |
190 | dcache->free_head = db; | |
191 | else | |
192 | dcache->free_tail->p = db; | |
193 | dcache->free_tail = db; | |
194 | db->p = 0; | |
195 | } | |
196 | ||
197 | dcache->cache_has_stuff = 0; | |
198 | ||
199 | return; | |
200 | } | |
201 | ||
202 | /* If addr is present in the dcache, return the address of the block | |
203 | containing it. */ | |
204 | ||
205 | static struct dcache_block * | |
fba45db2 | 206 | dcache_hit (DCACHE *dcache, CORE_ADDR addr) |
c906108c SS |
207 | { |
208 | register struct dcache_block *db; | |
209 | ||
210 | /* Search all cache blocks for one that is at this address. */ | |
211 | db = dcache->valid_head; | |
212 | ||
213 | while (db) | |
214 | { | |
c5aa993b | 215 | if (MASK (addr) == db->addr) |
c906108c SS |
216 | { |
217 | db->refs++; | |
218 | return db; | |
219 | } | |
220 | db = db->p; | |
221 | } | |
222 | ||
223 | return NULL; | |
224 | } | |
225 | ||
226 | /* Make sure that anything in this line which needs to | |
227 | be written is. */ | |
228 | ||
229 | static int | |
fba45db2 | 230 | dcache_write_line (DCACHE *dcache, register struct dcache_block *db) |
c906108c SS |
231 | { |
232 | int s; | |
233 | int e; | |
234 | s = 0; | |
235 | if (db->anydirty) | |
236 | { | |
237 | for (s = 0; s < LINE_SIZE; s++) | |
238 | { | |
239 | if (db->state[s] == ENTRY_DIRTY) | |
240 | { | |
241 | int len = 0; | |
c5aa993b | 242 | for (e = s; e < LINE_SIZE; e++, len++) |
c906108c SS |
243 | if (db->state[e] != ENTRY_DIRTY) |
244 | break; | |
245 | { | |
246 | /* all bytes from s..s+len-1 need to | |
247 | be written out */ | |
248 | int done = 0; | |
c5aa993b JM |
249 | while (done < len) |
250 | { | |
251 | int t = dcache->write_memory (db->addr + s + done, | |
252 | db->data + s + done, | |
253 | len - done); | |
254 | if (t == 0) | |
255 | return 0; | |
256 | done += t; | |
257 | } | |
c906108c SS |
258 | memset (db->state + s, ENTRY_OK, len); |
259 | s = e; | |
260 | } | |
261 | } | |
262 | } | |
263 | db->anydirty = 0; | |
264 | } | |
265 | return 1; | |
266 | } | |
267 | ||
268 | ||
269 | /* Get a free cache block, put or keep it on the valid list, | |
270 | and return its address. The caller should store into the block | |
271 | the address and data that it describes, then remque it from the | |
272 | free list and insert it into the valid list. This procedure | |
273 | prevents errors from creeping in if a memory retrieval is | |
274 | interrupted (which used to put garbage blocks in the valid | |
275 | list...). */ | |
276 | ||
277 | static struct dcache_block * | |
fba45db2 | 278 | dcache_alloc (DCACHE *dcache) |
c906108c SS |
279 | { |
280 | register struct dcache_block *db; | |
281 | ||
917317f4 | 282 | if (dcache_enabled_p == 0) |
c906108c SS |
283 | abort (); |
284 | ||
285 | /* Take something from the free list */ | |
286 | db = dcache->free_head; | |
287 | if (db) | |
288 | { | |
289 | dcache->free_head = db->p; | |
290 | } | |
291 | else | |
292 | { | |
293 | /* Nothing left on free list, so grab one from the valid list */ | |
294 | db = dcache->valid_head; | |
295 | dcache->valid_head = db->p; | |
296 | ||
297 | dcache_write_line (dcache, db); | |
298 | } | |
299 | ||
300 | /* append this line to end of valid list */ | |
301 | if (!dcache->valid_head) | |
302 | dcache->valid_head = db; | |
303 | else | |
304 | dcache->valid_tail->p = db; | |
305 | dcache->valid_tail = db; | |
306 | db->p = 0; | |
307 | ||
308 | return db; | |
309 | } | |
310 | ||
311 | /* Using the data cache DCACHE return the contents of the byte at | |
312 | address ADDR in the remote machine. | |
313 | ||
314 | Returns 0 on error. */ | |
315 | ||
316 | static int | |
fba45db2 | 317 | dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr) |
c906108c SS |
318 | { |
319 | register struct dcache_block *db = dcache_hit (dcache, addr); | |
c5aa993b | 320 | int ok = 1; |
c906108c SS |
321 | int done = 0; |
322 | if (db == 0 | |
323 | || db->state[XFORM (addr)] == ENTRY_BAD) | |
324 | { | |
325 | if (db) | |
326 | { | |
327 | dcache_write_line (dcache, db); | |
328 | } | |
c5aa993b JM |
329 | else |
330 | db = dcache_alloc (dcache); | |
c906108c SS |
331 | immediate_quit++; |
332 | db->addr = MASK (addr); | |
c5aa993b | 333 | while (done < LINE_SIZE) |
c906108c SS |
334 | { |
335 | int try = | |
c5aa993b JM |
336 | (*dcache->read_memory) |
337 | (db->addr + done, | |
338 | db->data + done, | |
339 | LINE_SIZE - done); | |
c906108c SS |
340 | if (try == 0) |
341 | return 0; | |
342 | done += try; | |
343 | } | |
344 | immediate_quit--; | |
c5aa993b | 345 | |
c906108c SS |
346 | memset (db->state, ENTRY_OK, sizeof (db->data)); |
347 | db->anydirty = 0; | |
348 | } | |
349 | *ptr = db->data[XFORM (addr)]; | |
350 | return ok; | |
351 | } | |
352 | ||
353 | /* Writeback any dirty lines to the remote. */ | |
354 | static int | |
fba45db2 | 355 | dcache_writeback (DCACHE *dcache) |
c906108c SS |
356 | { |
357 | struct dcache_block *db; | |
358 | ||
359 | db = dcache->valid_head; | |
360 | ||
361 | while (db) | |
362 | { | |
363 | if (!dcache_write_line (dcache, db)) | |
364 | return 0; | |
365 | db = db->p; | |
366 | } | |
367 | return 1; | |
368 | } | |
369 | ||
370 | ||
c906108c SS |
371 | /* Write the byte at PTR into ADDR in the data cache. |
372 | Return zero on write error. | |
373 | */ | |
374 | ||
375 | static int | |
fba45db2 | 376 | dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr) |
c906108c SS |
377 | { |
378 | register struct dcache_block *db = dcache_hit (dcache, addr); | |
379 | ||
380 | if (!db) | |
381 | { | |
382 | db = dcache_alloc (dcache); | |
383 | db->addr = MASK (addr); | |
384 | memset (db->state, ENTRY_BAD, sizeof (db->data)); | |
385 | } | |
386 | ||
387 | db->data[XFORM (addr)] = *ptr; | |
388 | db->state[XFORM (addr)] = ENTRY_DIRTY; | |
389 | db->anydirty = 1; | |
390 | return 1; | |
391 | } | |
392 | ||
c906108c SS |
393 | /* Initialize the data cache. */ |
394 | DCACHE * | |
fba45db2 | 395 | dcache_init (memxferfunc reading, memxferfunc writing) |
c906108c SS |
396 | { |
397 | int csize = sizeof (struct dcache_block) * DCACHE_SIZE; | |
398 | DCACHE *dcache; | |
399 | ||
400 | dcache = (DCACHE *) xmalloc (sizeof (*dcache)); | |
401 | dcache->read_memory = reading; | |
402 | dcache->write_memory = writing; | |
403 | ||
404 | dcache->the_cache = (struct dcache_block *) xmalloc (csize); | |
405 | memset (dcache->the_cache, 0, csize); | |
406 | ||
407 | dcache_flush (dcache); | |
408 | ||
409 | last_cache = dcache; | |
410 | return dcache; | |
411 | } | |
412 | ||
413 | /* Read or write LEN bytes from inferior memory at MEMADDR, transferring | |
414 | to or from debugger address MYADDR. Write to inferior if SHOULD_WRITE is | |
415 | nonzero. | |
416 | ||
417 | Returns length of data written or read; 0 for error. | |
418 | ||
419 | This routine is indended to be called by remote_xfer_ functions. */ | |
420 | ||
421 | int | |
fba45db2 KB |
422 | dcache_xfer_memory (DCACHE *dcache, CORE_ADDR memaddr, char *myaddr, int len, |
423 | int should_write) | |
c906108c SS |
424 | { |
425 | int i; | |
426 | ||
917317f4 | 427 | if (dcache_enabled_p) |
c906108c | 428 | { |
507f3c78 | 429 | int (*xfunc) (DCACHE * dcache, CORE_ADDR addr, char *ptr); |
c906108c SS |
430 | xfunc = should_write ? dcache_poke_byte : dcache_peek_byte; |
431 | ||
432 | for (i = 0; i < len; i++) | |
433 | { | |
434 | if (!xfunc (dcache, memaddr + i, myaddr + i)) | |
435 | return 0; | |
436 | } | |
437 | dcache->cache_has_stuff = 1; | |
438 | dcache_writeback (dcache); | |
439 | } | |
c5aa993b | 440 | else |
c906108c SS |
441 | { |
442 | memxferfunc xfunc; | |
443 | xfunc = should_write ? dcache->write_memory : dcache->read_memory; | |
444 | ||
445 | if (dcache->cache_has_stuff) | |
446 | dcache_flush (dcache); | |
447 | ||
448 | len = xfunc (memaddr, myaddr, len); | |
449 | } | |
450 | return len; | |
451 | } | |
452 | ||
c5aa993b | 453 | static void |
fba45db2 | 454 | dcache_info (char *exp, int tty) |
c906108c SS |
455 | { |
456 | struct dcache_block *p; | |
457 | ||
917317f4 | 458 | if (!dcache_enabled_p) |
c906108c SS |
459 | { |
460 | printf_filtered ("Dcache not enabled\n"); | |
461 | return; | |
462 | } | |
463 | printf_filtered ("Dcache enabled, line width %d, depth %d\n", | |
464 | LINE_SIZE, DCACHE_SIZE); | |
465 | ||
466 | printf_filtered ("Cache state:\n"); | |
467 | ||
468 | for (p = last_cache->valid_head; p; p = p->p) | |
469 | { | |
470 | int j; | |
d4f3574e SS |
471 | printf_filtered ("Line at %s, referenced %d times\n", |
472 | paddr (p->addr), p->refs); | |
c906108c SS |
473 | |
474 | for (j = 0; j < LINE_SIZE; j++) | |
475 | printf_filtered ("%02x", p->data[j] & 0xFF); | |
476 | printf_filtered ("\n"); | |
477 | ||
478 | for (j = 0; j < LINE_SIZE; j++) | |
479 | printf_filtered (" %2x", p->state[j]); | |
480 | printf_filtered ("\n"); | |
481 | } | |
482 | } | |
483 | ||
c2d11a7d JM |
484 | /* Turn dcache on or off. */ |
485 | void | |
486 | set_dcache_state (int what) | |
487 | { | |
488 | dcache_enabled_p = !!what; | |
489 | } | |
490 | ||
c906108c | 491 | void |
fba45db2 | 492 | _initialize_dcache (void) |
c906108c SS |
493 | { |
494 | add_show_from_set | |
495 | (add_set_cmd ("remotecache", class_support, var_boolean, | |
917317f4 | 496 | (char *) &dcache_enabled_p, |
c906108c SS |
497 | "\ |
498 | Set cache use for remote targets.\n\ | |
499 | When on, use data caching for remote targets. For many remote targets\n\ | |
500 | this option can offer better throughput for reading target memory.\n\ | |
501 | Unfortunately, gdb does not currently know anything about volatile\n\ | |
502 | registers and thus data caching will produce incorrect results with\n\ | |
917317f4 | 503 | volatile registers are in use. By default, this option is off.", |
c906108c SS |
504 | &setlist), |
505 | &showlist); | |
506 | ||
507 | add_info ("dcache", dcache_info, | |
508 | "Print information on the dcache performance."); | |
509 | ||
510 | } |