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a528910e JW |
1 | /* |
2 | * Workingset detection | |
3 | * | |
4 | * Copyright (C) 2013 Red Hat, Inc., Johannes Weiner | |
5 | */ | |
6 | ||
7 | #include <linux/memcontrol.h> | |
8 | #include <linux/writeback.h> | |
3a4f8a0b | 9 | #include <linux/shmem_fs.h> |
a528910e JW |
10 | #include <linux/pagemap.h> |
11 | #include <linux/atomic.h> | |
12 | #include <linux/module.h> | |
13 | #include <linux/swap.h> | |
14b46879 | 14 | #include <linux/dax.h> |
a528910e JW |
15 | #include <linux/fs.h> |
16 | #include <linux/mm.h> | |
17 | ||
18 | /* | |
19 | * Double CLOCK lists | |
20 | * | |
1e6b1085 | 21 | * Per node, two clock lists are maintained for file pages: the |
a528910e JW |
22 | * inactive and the active list. Freshly faulted pages start out at |
23 | * the head of the inactive list and page reclaim scans pages from the | |
24 | * tail. Pages that are accessed multiple times on the inactive list | |
25 | * are promoted to the active list, to protect them from reclaim, | |
26 | * whereas active pages are demoted to the inactive list when the | |
27 | * active list grows too big. | |
28 | * | |
29 | * fault ------------------------+ | |
30 | * | | |
31 | * +--------------+ | +-------------+ | |
32 | * reclaim <- | inactive | <-+-- demotion | active | <--+ | |
33 | * +--------------+ +-------------+ | | |
34 | * | | | |
35 | * +-------------- promotion ------------------+ | |
36 | * | |
37 | * | |
38 | * Access frequency and refault distance | |
39 | * | |
40 | * A workload is thrashing when its pages are frequently used but they | |
41 | * are evicted from the inactive list every time before another access | |
42 | * would have promoted them to the active list. | |
43 | * | |
44 | * In cases where the average access distance between thrashing pages | |
45 | * is bigger than the size of memory there is nothing that can be | |
46 | * done - the thrashing set could never fit into memory under any | |
47 | * circumstance. | |
48 | * | |
49 | * However, the average access distance could be bigger than the | |
50 | * inactive list, yet smaller than the size of memory. In this case, | |
51 | * the set could fit into memory if it weren't for the currently | |
52 | * active pages - which may be used more, hopefully less frequently: | |
53 | * | |
54 | * +-memory available to cache-+ | |
55 | * | | | |
56 | * +-inactive------+-active----+ | |
57 | * a b | c d e f g h i | J K L M N | | |
58 | * +---------------+-----------+ | |
59 | * | |
60 | * It is prohibitively expensive to accurately track access frequency | |
61 | * of pages. But a reasonable approximation can be made to measure | |
62 | * thrashing on the inactive list, after which refaulting pages can be | |
63 | * activated optimistically to compete with the existing active pages. | |
64 | * | |
65 | * Approximating inactive page access frequency - Observations: | |
66 | * | |
67 | * 1. When a page is accessed for the first time, it is added to the | |
68 | * head of the inactive list, slides every existing inactive page | |
69 | * towards the tail by one slot, and pushes the current tail page | |
70 | * out of memory. | |
71 | * | |
72 | * 2. When a page is accessed for the second time, it is promoted to | |
73 | * the active list, shrinking the inactive list by one slot. This | |
74 | * also slides all inactive pages that were faulted into the cache | |
75 | * more recently than the activated page towards the tail of the | |
76 | * inactive list. | |
77 | * | |
78 | * Thus: | |
79 | * | |
80 | * 1. The sum of evictions and activations between any two points in | |
81 | * time indicate the minimum number of inactive pages accessed in | |
82 | * between. | |
83 | * | |
84 | * 2. Moving one inactive page N page slots towards the tail of the | |
85 | * list requires at least N inactive page accesses. | |
86 | * | |
87 | * Combining these: | |
88 | * | |
89 | * 1. When a page is finally evicted from memory, the number of | |
90 | * inactive pages accessed while the page was in cache is at least | |
91 | * the number of page slots on the inactive list. | |
92 | * | |
93 | * 2. In addition, measuring the sum of evictions and activations (E) | |
94 | * at the time of a page's eviction, and comparing it to another | |
95 | * reading (R) at the time the page faults back into memory tells | |
96 | * the minimum number of accesses while the page was not cached. | |
97 | * This is called the refault distance. | |
98 | * | |
99 | * Because the first access of the page was the fault and the second | |
100 | * access the refault, we combine the in-cache distance with the | |
101 | * out-of-cache distance to get the complete minimum access distance | |
102 | * of this page: | |
103 | * | |
104 | * NR_inactive + (R - E) | |
105 | * | |
106 | * And knowing the minimum access distance of a page, we can easily | |
107 | * tell if the page would be able to stay in cache assuming all page | |
108 | * slots in the cache were available: | |
109 | * | |
110 | * NR_inactive + (R - E) <= NR_inactive + NR_active | |
111 | * | |
112 | * which can be further simplified to | |
113 | * | |
114 | * (R - E) <= NR_active | |
115 | * | |
116 | * Put into words, the refault distance (out-of-cache) can be seen as | |
117 | * a deficit in inactive list space (in-cache). If the inactive list | |
118 | * had (R - E) more page slots, the page would not have been evicted | |
119 | * in between accesses, but activated instead. And on a full system, | |
120 | * the only thing eating into inactive list space is active pages. | |
121 | * | |
122 | * | |
123 | * Activating refaulting pages | |
124 | * | |
125 | * All that is known about the active list is that the pages have been | |
126 | * accessed more than once in the past. This means that at any given | |
127 | * time there is actually a good chance that pages on the active list | |
128 | * are no longer in active use. | |
129 | * | |
130 | * So when a refault distance of (R - E) is observed and there are at | |
131 | * least (R - E) active pages, the refaulting page is activated | |
132 | * optimistically in the hope that (R - E) active pages are actually | |
133 | * used less frequently than the refaulting page - or even not used at | |
134 | * all anymore. | |
135 | * | |
136 | * If this is wrong and demotion kicks in, the pages which are truly | |
137 | * used more frequently will be reactivated while the less frequently | |
138 | * used once will be evicted from memory. | |
139 | * | |
140 | * But if this is right, the stale pages will be pushed out of memory | |
141 | * and the used pages get to stay in cache. | |
142 | * | |
143 | * | |
144 | * Implementation | |
145 | * | |
1e6b1085 MG |
146 | * For each node's file LRU lists, a counter for inactive evictions |
147 | * and activations is maintained (node->inactive_age). | |
a528910e JW |
148 | * |
149 | * On eviction, a snapshot of this counter (along with some bits to | |
1e6b1085 | 150 | * identify the node) is stored in the now empty page cache radix tree |
a528910e JW |
151 | * slot of the evicted page. This is called a shadow entry. |
152 | * | |
153 | * On cache misses for which there are shadow entries, an eligible | |
154 | * refault distance will immediately activate the refaulting page. | |
155 | */ | |
156 | ||
689c94f0 | 157 | #define EVICTION_SHIFT (RADIX_TREE_EXCEPTIONAL_ENTRY + \ |
1e6b1085 | 158 | NODES_SHIFT + \ |
23047a96 | 159 | MEM_CGROUP_ID_SHIFT) |
689c94f0 JW |
160 | #define EVICTION_MASK (~0UL >> EVICTION_SHIFT) |
161 | ||
612e4493 JW |
162 | /* |
163 | * Eviction timestamps need to be able to cover the full range of | |
164 | * actionable refaults. However, bits are tight in the radix tree | |
165 | * entry, and after storing the identifier for the lruvec there might | |
166 | * not be enough left to represent every single actionable refault. In | |
167 | * that case, we have to sacrifice granularity for distance, and group | |
168 | * evictions into coarser buckets by shaving off lower timestamp bits. | |
169 | */ | |
170 | static unsigned int bucket_order __read_mostly; | |
171 | ||
1e6b1085 | 172 | static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction) |
a528910e | 173 | { |
612e4493 | 174 | eviction >>= bucket_order; |
23047a96 | 175 | eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid; |
1e6b1085 | 176 | eviction = (eviction << NODES_SHIFT) | pgdat->node_id; |
a528910e JW |
177 | eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT); |
178 | ||
179 | return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY); | |
180 | } | |
181 | ||
1e6b1085 | 182 | static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, |
162453bf | 183 | unsigned long *evictionp) |
a528910e JW |
184 | { |
185 | unsigned long entry = (unsigned long)shadow; | |
1e6b1085 | 186 | int memcgid, nid; |
a528910e JW |
187 | |
188 | entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT; | |
a528910e JW |
189 | nid = entry & ((1UL << NODES_SHIFT) - 1); |
190 | entry >>= NODES_SHIFT; | |
23047a96 JW |
191 | memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1); |
192 | entry >>= MEM_CGROUP_ID_SHIFT; | |
a528910e | 193 | |
23047a96 | 194 | *memcgidp = memcgid; |
1e6b1085 | 195 | *pgdat = NODE_DATA(nid); |
612e4493 | 196 | *evictionp = entry << bucket_order; |
a528910e JW |
197 | } |
198 | ||
199 | /** | |
200 | * workingset_eviction - note the eviction of a page from memory | |
201 | * @mapping: address space the page was backing | |
202 | * @page: the page being evicted | |
203 | * | |
204 | * Returns a shadow entry to be stored in @mapping->page_tree in place | |
205 | * of the evicted @page so that a later refault can be detected. | |
206 | */ | |
207 | void *workingset_eviction(struct address_space *mapping, struct page *page) | |
208 | { | |
23047a96 | 209 | struct mem_cgroup *memcg = page_memcg(page); |
1e6b1085 | 210 | struct pglist_data *pgdat = page_pgdat(page); |
23047a96 | 211 | int memcgid = mem_cgroup_id(memcg); |
a528910e | 212 | unsigned long eviction; |
23047a96 | 213 | struct lruvec *lruvec; |
a528910e | 214 | |
23047a96 JW |
215 | /* Page is fully exclusive and pins page->mem_cgroup */ |
216 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
217 | VM_BUG_ON_PAGE(page_count(page), page); | |
218 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
219 | ||
1e6b1085 | 220 | lruvec = mem_cgroup_lruvec(pgdat, memcg); |
23047a96 | 221 | eviction = atomic_long_inc_return(&lruvec->inactive_age); |
1e6b1085 | 222 | return pack_shadow(memcgid, pgdat, eviction); |
a528910e JW |
223 | } |
224 | ||
225 | /** | |
226 | * workingset_refault - evaluate the refault of a previously evicted page | |
227 | * @shadow: shadow entry of the evicted page | |
228 | * | |
229 | * Calculates and evaluates the refault distance of the previously | |
1e6b1085 | 230 | * evicted page in the context of the node it was allocated in. |
a528910e JW |
231 | * |
232 | * Returns %true if the page should be activated, %false otherwise. | |
233 | */ | |
234 | bool workingset_refault(void *shadow) | |
235 | { | |
236 | unsigned long refault_distance; | |
23047a96 JW |
237 | unsigned long active_file; |
238 | struct mem_cgroup *memcg; | |
162453bf | 239 | unsigned long eviction; |
23047a96 | 240 | struct lruvec *lruvec; |
162453bf | 241 | unsigned long refault; |
1e6b1085 | 242 | struct pglist_data *pgdat; |
23047a96 | 243 | int memcgid; |
a528910e | 244 | |
1e6b1085 | 245 | unpack_shadow(shadow, &memcgid, &pgdat, &eviction); |
162453bf | 246 | |
23047a96 JW |
247 | rcu_read_lock(); |
248 | /* | |
249 | * Look up the memcg associated with the stored ID. It might | |
250 | * have been deleted since the page's eviction. | |
251 | * | |
252 | * Note that in rare events the ID could have been recycled | |
253 | * for a new cgroup that refaults a shared page. This is | |
254 | * impossible to tell from the available data. However, this | |
255 | * should be a rare and limited disturbance, and activations | |
256 | * are always speculative anyway. Ultimately, it's the aging | |
257 | * algorithm's job to shake out the minimum access frequency | |
258 | * for the active cache. | |
259 | * | |
260 | * XXX: On !CONFIG_MEMCG, this will always return NULL; it | |
261 | * would be better if the root_mem_cgroup existed in all | |
262 | * configurations instead. | |
263 | */ | |
264 | memcg = mem_cgroup_from_id(memcgid); | |
265 | if (!mem_cgroup_disabled() && !memcg) { | |
266 | rcu_read_unlock(); | |
267 | return false; | |
268 | } | |
1e6b1085 | 269 | lruvec = mem_cgroup_lruvec(pgdat, memcg); |
23047a96 | 270 | refault = atomic_long_read(&lruvec->inactive_age); |
fd538803 | 271 | active_file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES); |
162453bf JW |
272 | |
273 | /* | |
274 | * The unsigned subtraction here gives an accurate distance | |
275 | * across inactive_age overflows in most cases. | |
276 | * | |
277 | * There is a special case: usually, shadow entries have a | |
278 | * short lifetime and are either refaulted or reclaimed along | |
279 | * with the inode before they get too old. But it is not | |
280 | * impossible for the inactive_age to lap a shadow entry in | |
281 | * the field, which can then can result in a false small | |
282 | * refault distance, leading to a false activation should this | |
283 | * old entry actually refault again. However, earlier kernels | |
284 | * used to deactivate unconditionally with *every* reclaim | |
285 | * invocation for the longest time, so the occasional | |
286 | * inappropriate activation leading to pressure on the active | |
287 | * list is not a problem. | |
288 | */ | |
289 | refault_distance = (refault - eviction) & EVICTION_MASK; | |
290 | ||
1e6b1085 | 291 | inc_node_state(pgdat, WORKINGSET_REFAULT); |
ccda7f43 | 292 | inc_memcg_state(memcg, WORKINGSET_REFAULT); |
a528910e | 293 | |
23047a96 | 294 | if (refault_distance <= active_file) { |
1e6b1085 | 295 | inc_node_state(pgdat, WORKINGSET_ACTIVATE); |
ccda7f43 | 296 | inc_memcg_state(memcg, WORKINGSET_ACTIVATE); |
2a2e4885 | 297 | rcu_read_unlock(); |
a528910e JW |
298 | return true; |
299 | } | |
2a2e4885 | 300 | rcu_read_unlock(); |
a528910e JW |
301 | return false; |
302 | } | |
303 | ||
304 | /** | |
305 | * workingset_activation - note a page activation | |
306 | * @page: page that is being activated | |
307 | */ | |
308 | void workingset_activation(struct page *page) | |
309 | { | |
55779ec7 | 310 | struct mem_cgroup *memcg; |
23047a96 JW |
311 | struct lruvec *lruvec; |
312 | ||
55779ec7 | 313 | rcu_read_lock(); |
23047a96 JW |
314 | /* |
315 | * Filter non-memcg pages here, e.g. unmap can call | |
316 | * mark_page_accessed() on VDSO pages. | |
317 | * | |
318 | * XXX: See workingset_refault() - this should return | |
319 | * root_mem_cgroup even for !CONFIG_MEMCG. | |
320 | */ | |
55779ec7 JW |
321 | memcg = page_memcg_rcu(page); |
322 | if (!mem_cgroup_disabled() && !memcg) | |
23047a96 | 323 | goto out; |
ef8f2327 | 324 | lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg); |
23047a96 JW |
325 | atomic_long_inc(&lruvec->inactive_age); |
326 | out: | |
55779ec7 | 327 | rcu_read_unlock(); |
a528910e | 328 | } |
449dd698 JW |
329 | |
330 | /* | |
331 | * Shadow entries reflect the share of the working set that does not | |
332 | * fit into memory, so their number depends on the access pattern of | |
333 | * the workload. In most cases, they will refault or get reclaimed | |
334 | * along with the inode, but a (malicious) workload that streams | |
335 | * through files with a total size several times that of available | |
336 | * memory, while preventing the inodes from being reclaimed, can | |
337 | * create excessive amounts of shadow nodes. To keep a lid on this, | |
338 | * track shadow nodes and reclaim them when they grow way past the | |
339 | * point where they would still be useful. | |
340 | */ | |
341 | ||
14b46879 JW |
342 | static struct list_lru shadow_nodes; |
343 | ||
344 | void workingset_update_node(struct radix_tree_node *node, void *private) | |
345 | { | |
346 | struct address_space *mapping = private; | |
347 | ||
348 | /* Only regular page cache has shadow entries */ | |
349 | if (dax_mapping(mapping) || shmem_mapping(mapping)) | |
350 | return; | |
351 | ||
352 | /* | |
353 | * Track non-empty nodes that contain only shadow entries; | |
354 | * unlink those that contain pages or are being freed. | |
355 | * | |
356 | * Avoid acquiring the list_lru lock when the nodes are | |
357 | * already where they should be. The list_empty() test is safe | |
358 | * as node->private_list is protected by &mapping->tree_lock. | |
359 | */ | |
360 | if (node->count && node->count == node->exceptional) { | |
d58275bc | 361 | if (list_empty(&node->private_list)) |
14b46879 | 362 | list_lru_add(&shadow_nodes, &node->private_list); |
14b46879 JW |
363 | } else { |
364 | if (!list_empty(&node->private_list)) | |
365 | list_lru_del(&shadow_nodes, &node->private_list); | |
366 | } | |
367 | } | |
449dd698 JW |
368 | |
369 | static unsigned long count_shadow_nodes(struct shrinker *shrinker, | |
370 | struct shrink_control *sc) | |
371 | { | |
449dd698 | 372 | unsigned long max_nodes; |
14b46879 | 373 | unsigned long nodes; |
b5388998 | 374 | unsigned long cache; |
449dd698 JW |
375 | |
376 | /* list_lru lock nests inside IRQ-safe mapping->tree_lock */ | |
377 | local_irq_disable(); | |
14b46879 | 378 | nodes = list_lru_shrink_count(&shadow_nodes, sc); |
449dd698 JW |
379 | local_irq_enable(); |
380 | ||
449dd698 | 381 | /* |
b5388998 JW |
382 | * Approximate a reasonable limit for the radix tree nodes |
383 | * containing shadow entries. We don't need to keep more | |
384 | * shadow entries than possible pages on the active list, | |
385 | * since refault distances bigger than that are dismissed. | |
386 | * | |
387 | * The size of the active list converges toward 100% of | |
388 | * overall page cache as memory grows, with only a tiny | |
389 | * inactive list. Assume the total cache size for that. | |
390 | * | |
391 | * Nodes might be sparsely populated, with only one shadow | |
392 | * entry in the extreme case. Obviously, we cannot keep one | |
393 | * node for every eligible shadow entry, so compromise on a | |
394 | * worst-case density of 1/8th. Below that, not all eligible | |
395 | * refaults can be detected anymore. | |
449dd698 JW |
396 | * |
397 | * On 64-bit with 7 radix_tree_nodes per page and 64 slots | |
398 | * each, this will reclaim shadow entries when they consume | |
b5388998 | 399 | * ~1.8% of available memory: |
449dd698 | 400 | * |
b5388998 | 401 | * PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE |
449dd698 | 402 | */ |
b5388998 JW |
403 | if (sc->memcg) { |
404 | cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid, | |
405 | LRU_ALL_FILE); | |
406 | } else { | |
407 | cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) + | |
408 | node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE); | |
409 | } | |
410 | max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3); | |
449dd698 | 411 | |
14b46879 | 412 | if (nodes <= max_nodes) |
449dd698 | 413 | return 0; |
14b46879 | 414 | return nodes - max_nodes; |
449dd698 JW |
415 | } |
416 | ||
417 | static enum lru_status shadow_lru_isolate(struct list_head *item, | |
3f97b163 | 418 | struct list_lru_one *lru, |
449dd698 JW |
419 | spinlock_t *lru_lock, |
420 | void *arg) | |
421 | { | |
422 | struct address_space *mapping; | |
423 | struct radix_tree_node *node; | |
424 | unsigned int i; | |
425 | int ret; | |
426 | ||
427 | /* | |
428 | * Page cache insertions and deletions synchroneously maintain | |
429 | * the shadow node LRU under the mapping->tree_lock and the | |
430 | * lru_lock. Because the page cache tree is emptied before | |
431 | * the inode can be destroyed, holding the lru_lock pins any | |
432 | * address_space that has radix tree nodes on the LRU. | |
433 | * | |
434 | * We can then safely transition to the mapping->tree_lock to | |
435 | * pin only the address_space of the particular node we want | |
436 | * to reclaim, take the node off-LRU, and drop the lru_lock. | |
437 | */ | |
438 | ||
439 | node = container_of(item, struct radix_tree_node, private_list); | |
d58275bc | 440 | mapping = container_of(node->root, struct address_space, page_tree); |
449dd698 JW |
441 | |
442 | /* Coming from the list, invert the lock order */ | |
443 | if (!spin_trylock(&mapping->tree_lock)) { | |
444 | spin_unlock(lru_lock); | |
445 | ret = LRU_RETRY; | |
446 | goto out; | |
447 | } | |
448 | ||
3f97b163 | 449 | list_lru_isolate(lru, item); |
449dd698 JW |
450 | spin_unlock(lru_lock); |
451 | ||
452 | /* | |
453 | * The nodes should only contain one or more shadow entries, | |
454 | * no pages, so we expect to be able to remove them all and | |
455 | * delete and free the empty node afterwards. | |
456 | */ | |
14b46879 | 457 | if (WARN_ON_ONCE(!node->exceptional)) |
b936887e | 458 | goto out_invalid; |
14b46879 | 459 | if (WARN_ON_ONCE(node->count != node->exceptional)) |
b936887e | 460 | goto out_invalid; |
449dd698 JW |
461 | for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) { |
462 | if (node->slots[i]) { | |
b936887e JW |
463 | if (WARN_ON_ONCE(!radix_tree_exceptional_entry(node->slots[i]))) |
464 | goto out_invalid; | |
14b46879 JW |
465 | if (WARN_ON_ONCE(!node->exceptional)) |
466 | goto out_invalid; | |
b936887e JW |
467 | if (WARN_ON_ONCE(!mapping->nrexceptional)) |
468 | goto out_invalid; | |
449dd698 | 469 | node->slots[i] = NULL; |
14b46879 JW |
470 | node->exceptional--; |
471 | node->count--; | |
f9fe48be | 472 | mapping->nrexceptional--; |
449dd698 JW |
473 | } |
474 | } | |
14b46879 | 475 | if (WARN_ON_ONCE(node->exceptional)) |
b936887e | 476 | goto out_invalid; |
1e6b1085 | 477 | inc_node_state(page_pgdat(virt_to_page(node)), WORKINGSET_NODERECLAIM); |
ccda7f43 | 478 | inc_memcg_page_state(virt_to_page(node), WORKINGSET_NODERECLAIM); |
ea07b862 JW |
479 | __radix_tree_delete_node(&mapping->page_tree, node, |
480 | workingset_update_node, mapping); | |
449dd698 | 481 | |
b936887e | 482 | out_invalid: |
449dd698 JW |
483 | spin_unlock(&mapping->tree_lock); |
484 | ret = LRU_REMOVED_RETRY; | |
485 | out: | |
486 | local_irq_enable(); | |
487 | cond_resched(); | |
488 | local_irq_disable(); | |
489 | spin_lock(lru_lock); | |
490 | return ret; | |
491 | } | |
492 | ||
493 | static unsigned long scan_shadow_nodes(struct shrinker *shrinker, | |
494 | struct shrink_control *sc) | |
495 | { | |
496 | unsigned long ret; | |
497 | ||
498 | /* list_lru lock nests inside IRQ-safe mapping->tree_lock */ | |
499 | local_irq_disable(); | |
14b46879 | 500 | ret = list_lru_shrink_walk(&shadow_nodes, sc, shadow_lru_isolate, NULL); |
449dd698 JW |
501 | local_irq_enable(); |
502 | return ret; | |
503 | } | |
504 | ||
505 | static struct shrinker workingset_shadow_shrinker = { | |
506 | .count_objects = count_shadow_nodes, | |
507 | .scan_objects = scan_shadow_nodes, | |
508 | .seeks = DEFAULT_SEEKS, | |
0a6b76dd | 509 | .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, |
449dd698 JW |
510 | }; |
511 | ||
512 | /* | |
513 | * Our list_lru->lock is IRQ-safe as it nests inside the IRQ-safe | |
514 | * mapping->tree_lock. | |
515 | */ | |
516 | static struct lock_class_key shadow_nodes_key; | |
517 | ||
518 | static int __init workingset_init(void) | |
519 | { | |
612e4493 JW |
520 | unsigned int timestamp_bits; |
521 | unsigned int max_order; | |
449dd698 JW |
522 | int ret; |
523 | ||
612e4493 JW |
524 | BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT); |
525 | /* | |
526 | * Calculate the eviction bucket size to cover the longest | |
527 | * actionable refault distance, which is currently half of | |
528 | * memory (totalram_pages/2). However, memory hotplug may add | |
529 | * some more pages at runtime, so keep working with up to | |
530 | * double the initial memory by using totalram_pages as-is. | |
531 | */ | |
532 | timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT; | |
533 | max_order = fls_long(totalram_pages - 1); | |
534 | if (max_order > timestamp_bits) | |
535 | bucket_order = max_order - timestamp_bits; | |
d3d36c4b | 536 | pr_info("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n", |
612e4493 JW |
537 | timestamp_bits, max_order, bucket_order); |
538 | ||
0cefabda | 539 | ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key); |
449dd698 JW |
540 | if (ret) |
541 | goto err; | |
542 | ret = register_shrinker(&workingset_shadow_shrinker); | |
543 | if (ret) | |
544 | goto err_list_lru; | |
545 | return 0; | |
546 | err_list_lru: | |
14b46879 | 547 | list_lru_destroy(&shadow_nodes); |
449dd698 JW |
548 | err: |
549 | return ret; | |
550 | } | |
551 | module_init(workingset_init); |