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a50777c7 DM |
1 | /****************************************************************************** |
2 | * Xen selfballoon driver (and optional frontswap self-shrinking driver) | |
3 | * | |
4 | * Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp. | |
5 | * | |
6 | * This code complements the cleancache and frontswap patchsets to optimize | |
7 | * support for Xen Transcendent Memory ("tmem"). The policy it implements | |
8 | * is rudimentary and will likely improve over time, but it does work well | |
9 | * enough today. | |
10 | * | |
11 | * Two functionalities are implemented here which both use "control theory" | |
12 | * (feedback) to optimize memory utilization. In a virtualized environment | |
13 | * such as Xen, RAM is often a scarce resource and we would like to ensure | |
14 | * that each of a possibly large number of virtual machines is using RAM | |
15 | * efficiently, i.e. using as little as possible when under light load | |
16 | * and obtaining as much as possible when memory demands are high. | |
17 | * Since RAM needs vary highly dynamically and sometimes dramatically, | |
18 | * "hysteresis" is used, that is, memory target is determined not just | |
19 | * on current data but also on past data stored in the system. | |
20 | * | |
21 | * "Selfballooning" creates memory pressure by managing the Xen balloon | |
22 | * driver to decrease and increase available kernel memory, driven | |
23 | * largely by the target value of "Committed_AS" (see /proc/meminfo). | |
24 | * Since Committed_AS does not account for clean mapped pages (i.e. pages | |
25 | * in RAM that are identical to pages on disk), selfballooning has the | |
26 | * affect of pushing less frequently used clean pagecache pages out of | |
27 | * kernel RAM and, presumably using cleancache, into Xen tmem where | |
28 | * Xen can more efficiently optimize RAM utilization for such pages. | |
29 | * | |
30 | * When kernel memory demand unexpectedly increases faster than Xen, via | |
31 | * the selfballoon driver, is able to (or chooses to) provide usable RAM, | |
32 | * the kernel may invoke swapping. In most cases, frontswap is able | |
33 | * to absorb this swapping into Xen tmem. However, due to the fact | |
34 | * that the kernel swap subsystem assumes swapping occurs to a disk, | |
35 | * swapped pages may sit on the disk for a very long time; even if | |
36 | * the kernel knows the page will never be used again. This is because | |
37 | * the disk space costs very little and can be overwritten when | |
38 | * necessary. When such stale pages are in frontswap, however, they | |
39 | * are taking up valuable real estate. "Frontswap selfshrinking" works | |
40 | * to resolve this: When frontswap activity is otherwise stable | |
41 | * and the guest kernel is not under memory pressure, the "frontswap | |
42 | * selfshrinking" accounts for this by providing pressure to remove some | |
43 | * pages from frontswap and return them to kernel memory. | |
44 | * | |
45 | * For both "selfballooning" and "frontswap-selfshrinking", a worker | |
46 | * thread is used and sysfs tunables are provided to adjust the frequency | |
47 | * and rate of adjustments to achieve the goal, as well as to disable one | |
48 | * or both functions independently. | |
49 | * | |
50 | * While some argue that this functionality can and should be implemented | |
51 | * in userspace, it has been observed that bad things happen (e.g. OOMs). | |
52 | * | |
53 | * System configuration note: Selfballooning should not be enabled on | |
54 | * systems without a sufficiently large swap device configured; for best | |
55 | * results, it is recommended that total swap be increased by the size | |
56 | * of the guest memory. Also, while technically not required to be | |
57 | * configured, it is highly recommended that frontswap also be configured | |
58 | * and enabled when selfballooning is running. So, selfballooning | |
59 | * is disabled by default if frontswap is not configured and can only | |
60 | * be enabled with the "selfballooning" kernel boot option; similarly | |
61 | * selfballooning is enabled by default if frontswap is configured and | |
62 | * can be disabled with the "noselfballooning" kernel boot option. Finally, | |
63 | * when frontswap is configured, frontswap-selfshrinking can be disabled | |
64 | * with the "noselfshrink" kernel boot option. | |
65 | * | |
66 | * Selfballooning is disallowed in domain0 and force-disabled. | |
67 | * | |
68 | */ | |
69 | ||
70 | #include <linux/kernel.h> | |
38a1ed4f DM |
71 | #include <linux/bootmem.h> |
72 | #include <linux/swap.h> | |
a50777c7 DM |
73 | #include <linux/mm.h> |
74 | #include <linux/mman.h> | |
4fec0e0b | 75 | #include <linux/module.h> |
0642d2ed | 76 | #include <linux/workqueue.h> |
cb0c05c5 | 77 | #include <linux/device.h> |
a50777c7 | 78 | #include <xen/balloon.h> |
a50777c7 | 79 | #include <xen/tmem.h> |
0642d2ed | 80 | #include <xen/xen.h> |
a50777c7 DM |
81 | |
82 | /* Enable/disable with sysfs. */ | |
83 | static int xen_selfballooning_enabled __read_mostly; | |
84 | ||
85 | /* | |
86 | * Controls rate at which memory target (this iteration) approaches | |
87 | * ultimate goal when memory need is increasing (up-hysteresis) or | |
88 | * decreasing (down-hysteresis). Higher values of hysteresis cause | |
89 | * slower increases/decreases. The default values for the various | |
90 | * parameters were deemed reasonable by experimentation, may be | |
91 | * workload-dependent, and can all be adjusted via sysfs. | |
92 | */ | |
93 | static unsigned int selfballoon_downhysteresis __read_mostly = 8; | |
94 | static unsigned int selfballoon_uphysteresis __read_mostly = 1; | |
95 | ||
96 | /* In HZ, controls frequency of worker invocation. */ | |
97 | static unsigned int selfballoon_interval __read_mostly = 5; | |
98 | ||
38a1ed4f DM |
99 | /* |
100 | * Minimum usable RAM in MB for selfballooning target for balloon. | |
101 | * If non-zero, it is added to totalreserve_pages and self-ballooning | |
102 | * will not balloon below the sum. If zero, a piecewise linear function | |
103 | * is calculated as a minimum and added to totalreserve_pages. Note that | |
104 | * setting this value indiscriminately may cause OOMs and crashes. | |
105 | */ | |
106 | static unsigned int selfballoon_min_usable_mb; | |
107 | ||
a50777c7 DM |
108 | static void selfballoon_process(struct work_struct *work); |
109 | static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process); | |
110 | ||
111 | #ifdef CONFIG_FRONTSWAP | |
112 | #include <linux/frontswap.h> | |
113 | ||
114 | /* Enable/disable with sysfs. */ | |
115 | static bool frontswap_selfshrinking __read_mostly; | |
116 | ||
117 | /* Enable/disable with kernel boot option. */ | |
118 | static bool use_frontswap_selfshrink __initdata = true; | |
119 | ||
120 | /* | |
121 | * The default values for the following parameters were deemed reasonable | |
122 | * by experimentation, may be workload-dependent, and can all be | |
123 | * adjusted via sysfs. | |
124 | */ | |
125 | ||
126 | /* Control rate for frontswap shrinking. Higher hysteresis is slower. */ | |
127 | static unsigned int frontswap_hysteresis __read_mostly = 20; | |
128 | ||
129 | /* | |
130 | * Number of selfballoon worker invocations to wait before observing that | |
131 | * frontswap selfshrinking should commence. Note that selfshrinking does | |
132 | * not use a separate worker thread. | |
133 | */ | |
134 | static unsigned int frontswap_inertia __read_mostly = 3; | |
135 | ||
136 | /* Countdown to next invocation of frontswap_shrink() */ | |
137 | static unsigned long frontswap_inertia_counter; | |
138 | ||
139 | /* | |
140 | * Invoked by the selfballoon worker thread, uses current number of pages | |
141 | * in frontswap (frontswap_curr_pages()), previous status, and control | |
142 | * values (hysteresis and inertia) to determine if frontswap should be | |
143 | * shrunk and what the new frontswap size should be. Note that | |
144 | * frontswap_shrink is essentially a partial swapoff that immediately | |
145 | * transfers pages from the "swap device" (frontswap) back into kernel | |
146 | * RAM; despite the name, frontswap "shrinking" is very different from | |
147 | * the "shrinker" interface used by the kernel MM subsystem to reclaim | |
148 | * memory. | |
149 | */ | |
150 | static void frontswap_selfshrink(void) | |
151 | { | |
152 | static unsigned long cur_frontswap_pages; | |
153 | static unsigned long last_frontswap_pages; | |
154 | static unsigned long tgt_frontswap_pages; | |
155 | ||
156 | last_frontswap_pages = cur_frontswap_pages; | |
157 | cur_frontswap_pages = frontswap_curr_pages(); | |
158 | if (!cur_frontswap_pages || | |
159 | (cur_frontswap_pages > last_frontswap_pages)) { | |
160 | frontswap_inertia_counter = frontswap_inertia; | |
161 | return; | |
162 | } | |
163 | if (frontswap_inertia_counter && --frontswap_inertia_counter) | |
164 | return; | |
165 | if (cur_frontswap_pages <= frontswap_hysteresis) | |
166 | tgt_frontswap_pages = 0; | |
167 | else | |
168 | tgt_frontswap_pages = cur_frontswap_pages - | |
169 | (cur_frontswap_pages / frontswap_hysteresis); | |
170 | frontswap_shrink(tgt_frontswap_pages); | |
171 | } | |
172 | ||
173 | static int __init xen_nofrontswap_selfshrink_setup(char *s) | |
174 | { | |
175 | use_frontswap_selfshrink = false; | |
176 | return 1; | |
177 | } | |
178 | ||
179 | __setup("noselfshrink", xen_nofrontswap_selfshrink_setup); | |
180 | ||
181 | /* Disable with kernel boot option. */ | |
182 | static bool use_selfballooning __initdata = true; | |
183 | ||
184 | static int __init xen_noselfballooning_setup(char *s) | |
185 | { | |
186 | use_selfballooning = false; | |
187 | return 1; | |
188 | } | |
189 | ||
190 | __setup("noselfballooning", xen_noselfballooning_setup); | |
191 | #else /* !CONFIG_FRONTSWAP */ | |
192 | /* Enable with kernel boot option. */ | |
193 | static bool use_selfballooning __initdata = false; | |
194 | ||
195 | static int __init xen_selfballooning_setup(char *s) | |
196 | { | |
197 | use_selfballooning = true; | |
198 | return 1; | |
199 | } | |
200 | ||
201 | __setup("selfballooning", xen_selfballooning_setup); | |
202 | #endif /* CONFIG_FRONTSWAP */ | |
203 | ||
38a1ed4f DM |
204 | #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT)) |
205 | ||
a50777c7 DM |
206 | /* |
207 | * Use current balloon size, the goal (vm_committed_as), and hysteresis | |
208 | * parameters to set a new target balloon size | |
209 | */ | |
210 | static void selfballoon_process(struct work_struct *work) | |
211 | { | |
38a1ed4f DM |
212 | unsigned long cur_pages, goal_pages, tgt_pages, floor_pages; |
213 | unsigned long useful_pages; | |
a50777c7 DM |
214 | bool reset_timer = false; |
215 | ||
216 | if (xen_selfballooning_enabled) { | |
38a1ed4f | 217 | cur_pages = totalram_pages; |
a50777c7 DM |
218 | tgt_pages = cur_pages; /* default is no change */ |
219 | goal_pages = percpu_counter_read_positive(&vm_committed_as) + | |
38a1ed4f | 220 | totalreserve_pages; |
a50777c7 DM |
221 | #ifdef CONFIG_FRONTSWAP |
222 | /* allow space for frontswap pages to be repatriated */ | |
223 | if (frontswap_selfshrinking && frontswap_enabled) | |
224 | goal_pages += frontswap_curr_pages(); | |
225 | #endif | |
226 | if (cur_pages > goal_pages) | |
227 | tgt_pages = cur_pages - | |
228 | ((cur_pages - goal_pages) / | |
229 | selfballoon_downhysteresis); | |
230 | else if (cur_pages < goal_pages) | |
231 | tgt_pages = cur_pages + | |
232 | ((goal_pages - cur_pages) / | |
233 | selfballoon_uphysteresis); | |
234 | /* else if cur_pages == goal_pages, no change */ | |
38a1ed4f DM |
235 | useful_pages = max_pfn - totalreserve_pages; |
236 | if (selfballoon_min_usable_mb != 0) | |
237 | floor_pages = totalreserve_pages + | |
238 | MB2PAGES(selfballoon_min_usable_mb); | |
239 | /* piecewise linear function ending in ~3% slope */ | |
240 | else if (useful_pages < MB2PAGES(16)) | |
241 | floor_pages = max_pfn; /* not worth ballooning */ | |
242 | else if (useful_pages < MB2PAGES(64)) | |
243 | floor_pages = totalreserve_pages + MB2PAGES(16) + | |
244 | ((useful_pages - MB2PAGES(16)) >> 1); | |
245 | else if (useful_pages < MB2PAGES(512)) | |
246 | floor_pages = totalreserve_pages + MB2PAGES(40) + | |
247 | ((useful_pages - MB2PAGES(40)) >> 3); | |
248 | else /* useful_pages >= MB2PAGES(512) */ | |
249 | floor_pages = totalreserve_pages + MB2PAGES(99) + | |
250 | ((useful_pages - MB2PAGES(99)) >> 5); | |
251 | if (tgt_pages < floor_pages) | |
252 | tgt_pages = floor_pages; | |
253 | balloon_set_new_target(tgt_pages + | |
254 | balloon_stats.current_pages - totalram_pages); | |
a50777c7 DM |
255 | reset_timer = true; |
256 | } | |
257 | #ifdef CONFIG_FRONTSWAP | |
258 | if (frontswap_selfshrinking && frontswap_enabled) { | |
259 | frontswap_selfshrink(); | |
260 | reset_timer = true; | |
261 | } | |
262 | #endif | |
263 | if (reset_timer) | |
264 | schedule_delayed_work(&selfballoon_worker, | |
265 | selfballoon_interval * HZ); | |
266 | } | |
267 | ||
268 | #ifdef CONFIG_SYSFS | |
269 | ||
a50777c7 DM |
270 | #include <linux/capability.h> |
271 | ||
272 | #define SELFBALLOON_SHOW(name, format, args...) \ | |
07068021 KS |
273 | static ssize_t show_##name(struct device *dev, \ |
274 | struct device_attribute *attr, \ | |
275 | char *buf) \ | |
a50777c7 DM |
276 | { \ |
277 | return sprintf(buf, format, ##args); \ | |
278 | } | |
279 | ||
280 | SELFBALLOON_SHOW(selfballooning, "%d\n", xen_selfballooning_enabled); | |
281 | ||
07068021 KS |
282 | static ssize_t store_selfballooning(struct device *dev, |
283 | struct device_attribute *attr, | |
a50777c7 DM |
284 | const char *buf, |
285 | size_t count) | |
286 | { | |
287 | bool was_enabled = xen_selfballooning_enabled; | |
288 | unsigned long tmp; | |
289 | int err; | |
290 | ||
291 | if (!capable(CAP_SYS_ADMIN)) | |
292 | return -EPERM; | |
293 | ||
294 | err = strict_strtoul(buf, 10, &tmp); | |
295 | if (err || ((tmp != 0) && (tmp != 1))) | |
296 | return -EINVAL; | |
297 | ||
298 | xen_selfballooning_enabled = !!tmp; | |
299 | if (!was_enabled && xen_selfballooning_enabled) | |
300 | schedule_delayed_work(&selfballoon_worker, | |
301 | selfballoon_interval * HZ); | |
302 | ||
303 | return count; | |
304 | } | |
305 | ||
07068021 | 306 | static DEVICE_ATTR(selfballooning, S_IRUGO | S_IWUSR, |
a50777c7 DM |
307 | show_selfballooning, store_selfballooning); |
308 | ||
309 | SELFBALLOON_SHOW(selfballoon_interval, "%d\n", selfballoon_interval); | |
310 | ||
07068021 KS |
311 | static ssize_t store_selfballoon_interval(struct device *dev, |
312 | struct device_attribute *attr, | |
a50777c7 DM |
313 | const char *buf, |
314 | size_t count) | |
315 | { | |
316 | unsigned long val; | |
317 | int err; | |
318 | ||
319 | if (!capable(CAP_SYS_ADMIN)) | |
320 | return -EPERM; | |
321 | err = strict_strtoul(buf, 10, &val); | |
322 | if (err || val == 0) | |
323 | return -EINVAL; | |
324 | selfballoon_interval = val; | |
325 | return count; | |
326 | } | |
327 | ||
07068021 | 328 | static DEVICE_ATTR(selfballoon_interval, S_IRUGO | S_IWUSR, |
a50777c7 DM |
329 | show_selfballoon_interval, store_selfballoon_interval); |
330 | ||
331 | SELFBALLOON_SHOW(selfballoon_downhys, "%d\n", selfballoon_downhysteresis); | |
332 | ||
07068021 KS |
333 | static ssize_t store_selfballoon_downhys(struct device *dev, |
334 | struct device_attribute *attr, | |
a50777c7 DM |
335 | const char *buf, |
336 | size_t count) | |
337 | { | |
338 | unsigned long val; | |
339 | int err; | |
340 | ||
341 | if (!capable(CAP_SYS_ADMIN)) | |
342 | return -EPERM; | |
343 | err = strict_strtoul(buf, 10, &val); | |
344 | if (err || val == 0) | |
345 | return -EINVAL; | |
346 | selfballoon_downhysteresis = val; | |
347 | return count; | |
348 | } | |
349 | ||
07068021 | 350 | static DEVICE_ATTR(selfballoon_downhysteresis, S_IRUGO | S_IWUSR, |
a50777c7 DM |
351 | show_selfballoon_downhys, store_selfballoon_downhys); |
352 | ||
353 | ||
354 | SELFBALLOON_SHOW(selfballoon_uphys, "%d\n", selfballoon_uphysteresis); | |
355 | ||
07068021 KS |
356 | static ssize_t store_selfballoon_uphys(struct device *dev, |
357 | struct device_attribute *attr, | |
a50777c7 DM |
358 | const char *buf, |
359 | size_t count) | |
360 | { | |
361 | unsigned long val; | |
362 | int err; | |
363 | ||
364 | if (!capable(CAP_SYS_ADMIN)) | |
365 | return -EPERM; | |
366 | err = strict_strtoul(buf, 10, &val); | |
367 | if (err || val == 0) | |
368 | return -EINVAL; | |
369 | selfballoon_uphysteresis = val; | |
370 | return count; | |
371 | } | |
372 | ||
07068021 | 373 | static DEVICE_ATTR(selfballoon_uphysteresis, S_IRUGO | S_IWUSR, |
a50777c7 DM |
374 | show_selfballoon_uphys, store_selfballoon_uphys); |
375 | ||
38a1ed4f DM |
376 | SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n", |
377 | selfballoon_min_usable_mb); | |
378 | ||
07068021 KS |
379 | static ssize_t store_selfballoon_min_usable_mb(struct device *dev, |
380 | struct device_attribute *attr, | |
38a1ed4f DM |
381 | const char *buf, |
382 | size_t count) | |
383 | { | |
384 | unsigned long val; | |
385 | int err; | |
386 | ||
387 | if (!capable(CAP_SYS_ADMIN)) | |
388 | return -EPERM; | |
389 | err = strict_strtoul(buf, 10, &val); | |
390 | if (err || val == 0) | |
391 | return -EINVAL; | |
392 | selfballoon_min_usable_mb = val; | |
393 | return count; | |
394 | } | |
395 | ||
07068021 | 396 | static DEVICE_ATTR(selfballoon_min_usable_mb, S_IRUGO | S_IWUSR, |
38a1ed4f DM |
397 | show_selfballoon_min_usable_mb, |
398 | store_selfballoon_min_usable_mb); | |
399 | ||
400 | ||
a50777c7 DM |
401 | #ifdef CONFIG_FRONTSWAP |
402 | SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking); | |
403 | ||
07068021 KS |
404 | static ssize_t store_frontswap_selfshrinking(struct device *dev, |
405 | struct device_attribute *attr, | |
a50777c7 DM |
406 | const char *buf, |
407 | size_t count) | |
408 | { | |
409 | bool was_enabled = frontswap_selfshrinking; | |
410 | unsigned long tmp; | |
411 | int err; | |
412 | ||
413 | if (!capable(CAP_SYS_ADMIN)) | |
414 | return -EPERM; | |
415 | err = strict_strtoul(buf, 10, &tmp); | |
416 | if (err || ((tmp != 0) && (tmp != 1))) | |
417 | return -EINVAL; | |
418 | frontswap_selfshrinking = !!tmp; | |
419 | if (!was_enabled && !xen_selfballooning_enabled && | |
420 | frontswap_selfshrinking) | |
421 | schedule_delayed_work(&selfballoon_worker, | |
422 | selfballoon_interval * HZ); | |
423 | ||
424 | return count; | |
425 | } | |
426 | ||
07068021 | 427 | static DEVICE_ATTR(frontswap_selfshrinking, S_IRUGO | S_IWUSR, |
a50777c7 DM |
428 | show_frontswap_selfshrinking, store_frontswap_selfshrinking); |
429 | ||
430 | SELFBALLOON_SHOW(frontswap_inertia, "%d\n", frontswap_inertia); | |
431 | ||
07068021 KS |
432 | static ssize_t store_frontswap_inertia(struct device *dev, |
433 | struct device_attribute *attr, | |
a50777c7 DM |
434 | const char *buf, |
435 | size_t count) | |
436 | { | |
437 | unsigned long val; | |
438 | int err; | |
439 | ||
440 | if (!capable(CAP_SYS_ADMIN)) | |
441 | return -EPERM; | |
442 | err = strict_strtoul(buf, 10, &val); | |
443 | if (err || val == 0) | |
444 | return -EINVAL; | |
445 | frontswap_inertia = val; | |
446 | frontswap_inertia_counter = val; | |
447 | return count; | |
448 | } | |
449 | ||
07068021 | 450 | static DEVICE_ATTR(frontswap_inertia, S_IRUGO | S_IWUSR, |
a50777c7 DM |
451 | show_frontswap_inertia, store_frontswap_inertia); |
452 | ||
453 | SELFBALLOON_SHOW(frontswap_hysteresis, "%d\n", frontswap_hysteresis); | |
454 | ||
07068021 KS |
455 | static ssize_t store_frontswap_hysteresis(struct device *dev, |
456 | struct device_attribute *attr, | |
a50777c7 DM |
457 | const char *buf, |
458 | size_t count) | |
459 | { | |
460 | unsigned long val; | |
461 | int err; | |
462 | ||
463 | if (!capable(CAP_SYS_ADMIN)) | |
464 | return -EPERM; | |
465 | err = strict_strtoul(buf, 10, &val); | |
466 | if (err || val == 0) | |
467 | return -EINVAL; | |
468 | frontswap_hysteresis = val; | |
469 | return count; | |
470 | } | |
471 | ||
07068021 | 472 | static DEVICE_ATTR(frontswap_hysteresis, S_IRUGO | S_IWUSR, |
a50777c7 DM |
473 | show_frontswap_hysteresis, store_frontswap_hysteresis); |
474 | ||
475 | #endif /* CONFIG_FRONTSWAP */ | |
476 | ||
477 | static struct attribute *selfballoon_attrs[] = { | |
07068021 KS |
478 | &dev_attr_selfballooning.attr, |
479 | &dev_attr_selfballoon_interval.attr, | |
480 | &dev_attr_selfballoon_downhysteresis.attr, | |
481 | &dev_attr_selfballoon_uphysteresis.attr, | |
482 | &dev_attr_selfballoon_min_usable_mb.attr, | |
a50777c7 | 483 | #ifdef CONFIG_FRONTSWAP |
07068021 KS |
484 | &dev_attr_frontswap_selfshrinking.attr, |
485 | &dev_attr_frontswap_hysteresis.attr, | |
486 | &dev_attr_frontswap_inertia.attr, | |
a50777c7 DM |
487 | #endif |
488 | NULL | |
489 | }; | |
490 | ||
ead1d014 | 491 | static const struct attribute_group selfballoon_group = { |
a50777c7 DM |
492 | .name = "selfballoon", |
493 | .attrs = selfballoon_attrs | |
494 | }; | |
495 | #endif | |
496 | ||
07068021 | 497 | int register_xen_selfballooning(struct device *dev) |
a50777c7 DM |
498 | { |
499 | int error = -1; | |
500 | ||
501 | #ifdef CONFIG_SYSFS | |
07068021 | 502 | error = sysfs_create_group(&dev->kobj, &selfballoon_group); |
a50777c7 DM |
503 | #endif |
504 | return error; | |
505 | } | |
506 | EXPORT_SYMBOL(register_xen_selfballooning); | |
507 | ||
508 | static int __init xen_selfballoon_init(void) | |
509 | { | |
510 | bool enable = false; | |
511 | ||
512 | if (!xen_domain()) | |
513 | return -ENODEV; | |
514 | ||
515 | if (xen_initial_domain()) { | |
516 | pr_info("xen/balloon: Xen selfballooning driver " | |
517 | "disabled for domain0.\n"); | |
518 | return -ENODEV; | |
519 | } | |
520 | ||
521 | xen_selfballooning_enabled = tmem_enabled && use_selfballooning; | |
522 | if (xen_selfballooning_enabled) { | |
523 | pr_info("xen/balloon: Initializing Xen " | |
524 | "selfballooning driver.\n"); | |
525 | enable = true; | |
526 | } | |
527 | #ifdef CONFIG_FRONTSWAP | |
528 | frontswap_selfshrinking = tmem_enabled && use_frontswap_selfshrink; | |
529 | if (frontswap_selfshrinking) { | |
530 | pr_info("xen/balloon: Initializing frontswap " | |
531 | "selfshrinking driver.\n"); | |
532 | enable = true; | |
533 | } | |
534 | #endif | |
535 | if (!enable) | |
536 | return -ENODEV; | |
537 | ||
538 | schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ); | |
539 | ||
540 | return 0; | |
541 | } | |
542 | ||
543 | subsys_initcall(xen_selfballoon_init); | |
544 | ||
545 | MODULE_LICENSE("GPL"); |