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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
a528910e JW |
2 | /* |
3 | * Workingset detection | |
4 | * | |
5 | * Copyright (C) 2013 Red Hat, Inc., Johannes Weiner | |
6 | */ | |
7 | ||
8 | #include <linux/memcontrol.h> | |
9 | #include <linux/writeback.h> | |
3a4f8a0b | 10 | #include <linux/shmem_fs.h> |
a528910e JW |
11 | #include <linux/pagemap.h> |
12 | #include <linux/atomic.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/swap.h> | |
14b46879 | 15 | #include <linux/dax.h> |
a528910e JW |
16 | #include <linux/fs.h> |
17 | #include <linux/mm.h> | |
18 | ||
19 | /* | |
20 | * Double CLOCK lists | |
21 | * | |
1e6b1085 | 22 | * Per node, two clock lists are maintained for file pages: the |
a528910e JW |
23 | * inactive and the active list. Freshly faulted pages start out at |
24 | * the head of the inactive list and page reclaim scans pages from the | |
25 | * tail. Pages that are accessed multiple times on the inactive list | |
26 | * are promoted to the active list, to protect them from reclaim, | |
27 | * whereas active pages are demoted to the inactive list when the | |
28 | * active list grows too big. | |
29 | * | |
30 | * fault ------------------------+ | |
31 | * | | |
32 | * +--------------+ | +-------------+ | |
33 | * reclaim <- | inactive | <-+-- demotion | active | <--+ | |
34 | * +--------------+ +-------------+ | | |
35 | * | | | |
36 | * +-------------- promotion ------------------+ | |
37 | * | |
38 | * | |
39 | * Access frequency and refault distance | |
40 | * | |
41 | * A workload is thrashing when its pages are frequently used but they | |
42 | * are evicted from the inactive list every time before another access | |
43 | * would have promoted them to the active list. | |
44 | * | |
45 | * In cases where the average access distance between thrashing pages | |
46 | * is bigger than the size of memory there is nothing that can be | |
47 | * done - the thrashing set could never fit into memory under any | |
48 | * circumstance. | |
49 | * | |
50 | * However, the average access distance could be bigger than the | |
51 | * inactive list, yet smaller than the size of memory. In this case, | |
52 | * the set could fit into memory if it weren't for the currently | |
53 | * active pages - which may be used more, hopefully less frequently: | |
54 | * | |
55 | * +-memory available to cache-+ | |
56 | * | | | |
57 | * +-inactive------+-active----+ | |
58 | * a b | c d e f g h i | J K L M N | | |
59 | * +---------------+-----------+ | |
60 | * | |
61 | * It is prohibitively expensive to accurately track access frequency | |
62 | * of pages. But a reasonable approximation can be made to measure | |
63 | * thrashing on the inactive list, after which refaulting pages can be | |
64 | * activated optimistically to compete with the existing active pages. | |
65 | * | |
66 | * Approximating inactive page access frequency - Observations: | |
67 | * | |
68 | * 1. When a page is accessed for the first time, it is added to the | |
69 | * head of the inactive list, slides every existing inactive page | |
70 | * towards the tail by one slot, and pushes the current tail page | |
71 | * out of memory. | |
72 | * | |
73 | * 2. When a page is accessed for the second time, it is promoted to | |
74 | * the active list, shrinking the inactive list by one slot. This | |
75 | * also slides all inactive pages that were faulted into the cache | |
76 | * more recently than the activated page towards the tail of the | |
77 | * inactive list. | |
78 | * | |
79 | * Thus: | |
80 | * | |
81 | * 1. The sum of evictions and activations between any two points in | |
82 | * time indicate the minimum number of inactive pages accessed in | |
83 | * between. | |
84 | * | |
85 | * 2. Moving one inactive page N page slots towards the tail of the | |
86 | * list requires at least N inactive page accesses. | |
87 | * | |
88 | * Combining these: | |
89 | * | |
90 | * 1. When a page is finally evicted from memory, the number of | |
91 | * inactive pages accessed while the page was in cache is at least | |
92 | * the number of page slots on the inactive list. | |
93 | * | |
94 | * 2. In addition, measuring the sum of evictions and activations (E) | |
95 | * at the time of a page's eviction, and comparing it to another | |
96 | * reading (R) at the time the page faults back into memory tells | |
97 | * the minimum number of accesses while the page was not cached. | |
98 | * This is called the refault distance. | |
99 | * | |
100 | * Because the first access of the page was the fault and the second | |
101 | * access the refault, we combine the in-cache distance with the | |
102 | * out-of-cache distance to get the complete minimum access distance | |
103 | * of this page: | |
104 | * | |
105 | * NR_inactive + (R - E) | |
106 | * | |
107 | * And knowing the minimum access distance of a page, we can easily | |
108 | * tell if the page would be able to stay in cache assuming all page | |
109 | * slots in the cache were available: | |
110 | * | |
111 | * NR_inactive + (R - E) <= NR_inactive + NR_active | |
112 | * | |
113 | * which can be further simplified to | |
114 | * | |
115 | * (R - E) <= NR_active | |
116 | * | |
117 | * Put into words, the refault distance (out-of-cache) can be seen as | |
118 | * a deficit in inactive list space (in-cache). If the inactive list | |
119 | * had (R - E) more page slots, the page would not have been evicted | |
120 | * in between accesses, but activated instead. And on a full system, | |
121 | * the only thing eating into inactive list space is active pages. | |
122 | * | |
123 | * | |
1899ad18 | 124 | * Refaulting inactive pages |
a528910e JW |
125 | * |
126 | * All that is known about the active list is that the pages have been | |
127 | * accessed more than once in the past. This means that at any given | |
128 | * time there is actually a good chance that pages on the active list | |
129 | * are no longer in active use. | |
130 | * | |
131 | * So when a refault distance of (R - E) is observed and there are at | |
132 | * least (R - E) active pages, the refaulting page is activated | |
133 | * optimistically in the hope that (R - E) active pages are actually | |
134 | * used less frequently than the refaulting page - or even not used at | |
135 | * all anymore. | |
136 | * | |
1899ad18 JW |
137 | * That means if inactive cache is refaulting with a suitable refault |
138 | * distance, we assume the cache workingset is transitioning and put | |
139 | * pressure on the current active list. | |
140 | * | |
a528910e JW |
141 | * If this is wrong and demotion kicks in, the pages which are truly |
142 | * used more frequently will be reactivated while the less frequently | |
143 | * used once will be evicted from memory. | |
144 | * | |
145 | * But if this is right, the stale pages will be pushed out of memory | |
146 | * and the used pages get to stay in cache. | |
147 | * | |
1899ad18 JW |
148 | * Refaulting active pages |
149 | * | |
150 | * If on the other hand the refaulting pages have recently been | |
151 | * deactivated, it means that the active list is no longer protecting | |
152 | * actively used cache from reclaim. The cache is NOT transitioning to | |
153 | * a different workingset; the existing workingset is thrashing in the | |
154 | * space allocated to the page cache. | |
155 | * | |
a528910e JW |
156 | * |
157 | * Implementation | |
158 | * | |
1e6b1085 MG |
159 | * For each node's file LRU lists, a counter for inactive evictions |
160 | * and activations is maintained (node->inactive_age). | |
a528910e JW |
161 | * |
162 | * On eviction, a snapshot of this counter (along with some bits to | |
a97e7904 | 163 | * identify the node) is stored in the now empty page cache |
a528910e JW |
164 | * slot of the evicted page. This is called a shadow entry. |
165 | * | |
166 | * On cache misses for which there are shadow entries, an eligible | |
167 | * refault distance will immediately activate the refaulting page. | |
168 | */ | |
169 | ||
3159f943 | 170 | #define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \ |
1899ad18 | 171 | 1 + NODES_SHIFT + MEM_CGROUP_ID_SHIFT) |
689c94f0 JW |
172 | #define EVICTION_MASK (~0UL >> EVICTION_SHIFT) |
173 | ||
612e4493 JW |
174 | /* |
175 | * Eviction timestamps need to be able to cover the full range of | |
a97e7904 | 176 | * actionable refaults. However, bits are tight in the xarray |
612e4493 JW |
177 | * entry, and after storing the identifier for the lruvec there might |
178 | * not be enough left to represent every single actionable refault. In | |
179 | * that case, we have to sacrifice granularity for distance, and group | |
180 | * evictions into coarser buckets by shaving off lower timestamp bits. | |
181 | */ | |
182 | static unsigned int bucket_order __read_mostly; | |
183 | ||
1899ad18 JW |
184 | static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction, |
185 | bool workingset) | |
a528910e | 186 | { |
612e4493 | 187 | eviction >>= bucket_order; |
3159f943 | 188 | eviction &= EVICTION_MASK; |
23047a96 | 189 | eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid; |
1e6b1085 | 190 | eviction = (eviction << NODES_SHIFT) | pgdat->node_id; |
1899ad18 | 191 | eviction = (eviction << 1) | workingset; |
a528910e | 192 | |
3159f943 | 193 | return xa_mk_value(eviction); |
a528910e JW |
194 | } |
195 | ||
1e6b1085 | 196 | static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, |
1899ad18 | 197 | unsigned long *evictionp, bool *workingsetp) |
a528910e | 198 | { |
3159f943 | 199 | unsigned long entry = xa_to_value(shadow); |
1e6b1085 | 200 | int memcgid, nid; |
1899ad18 | 201 | bool workingset; |
a528910e | 202 | |
1899ad18 JW |
203 | workingset = entry & 1; |
204 | entry >>= 1; | |
a528910e JW |
205 | nid = entry & ((1UL << NODES_SHIFT) - 1); |
206 | entry >>= NODES_SHIFT; | |
23047a96 JW |
207 | memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1); |
208 | entry >>= MEM_CGROUP_ID_SHIFT; | |
a528910e | 209 | |
23047a96 | 210 | *memcgidp = memcgid; |
1e6b1085 | 211 | *pgdat = NODE_DATA(nid); |
612e4493 | 212 | *evictionp = entry << bucket_order; |
1899ad18 | 213 | *workingsetp = workingset; |
a528910e JW |
214 | } |
215 | ||
216 | /** | |
217 | * workingset_eviction - note the eviction of a page from memory | |
a528910e JW |
218 | * @page: the page being evicted |
219 | * | |
a7ca12f9 | 220 | * Returns a shadow entry to be stored in @page->mapping->i_pages in place |
a528910e JW |
221 | * of the evicted @page so that a later refault can be detected. |
222 | */ | |
a7ca12f9 | 223 | void *workingset_eviction(struct page *page) |
a528910e | 224 | { |
1e6b1085 | 225 | struct pglist_data *pgdat = page_pgdat(page); |
1899ad18 | 226 | struct mem_cgroup *memcg = page_memcg(page); |
23047a96 | 227 | int memcgid = mem_cgroup_id(memcg); |
a528910e | 228 | unsigned long eviction; |
23047a96 | 229 | struct lruvec *lruvec; |
a528910e | 230 | |
23047a96 JW |
231 | /* Page is fully exclusive and pins page->mem_cgroup */ |
232 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
233 | VM_BUG_ON_PAGE(page_count(page), page); | |
234 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
235 | ||
1e6b1085 | 236 | lruvec = mem_cgroup_lruvec(pgdat, memcg); |
23047a96 | 237 | eviction = atomic_long_inc_return(&lruvec->inactive_age); |
1899ad18 | 238 | return pack_shadow(memcgid, pgdat, eviction, PageWorkingset(page)); |
a528910e JW |
239 | } |
240 | ||
241 | /** | |
242 | * workingset_refault - evaluate the refault of a previously evicted page | |
1899ad18 | 243 | * @page: the freshly allocated replacement page |
a528910e JW |
244 | * @shadow: shadow entry of the evicted page |
245 | * | |
246 | * Calculates and evaluates the refault distance of the previously | |
1e6b1085 | 247 | * evicted page in the context of the node it was allocated in. |
a528910e | 248 | */ |
1899ad18 | 249 | void workingset_refault(struct page *page, void *shadow) |
a528910e JW |
250 | { |
251 | unsigned long refault_distance; | |
1899ad18 | 252 | struct pglist_data *pgdat; |
23047a96 JW |
253 | unsigned long active_file; |
254 | struct mem_cgroup *memcg; | |
162453bf | 255 | unsigned long eviction; |
23047a96 | 256 | struct lruvec *lruvec; |
162453bf | 257 | unsigned long refault; |
1899ad18 | 258 | bool workingset; |
23047a96 | 259 | int memcgid; |
a528910e | 260 | |
1899ad18 | 261 | unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset); |
162453bf | 262 | |
23047a96 JW |
263 | rcu_read_lock(); |
264 | /* | |
265 | * Look up the memcg associated with the stored ID. It might | |
266 | * have been deleted since the page's eviction. | |
267 | * | |
268 | * Note that in rare events the ID could have been recycled | |
269 | * for a new cgroup that refaults a shared page. This is | |
270 | * impossible to tell from the available data. However, this | |
271 | * should be a rare and limited disturbance, and activations | |
272 | * are always speculative anyway. Ultimately, it's the aging | |
273 | * algorithm's job to shake out the minimum access frequency | |
274 | * for the active cache. | |
275 | * | |
276 | * XXX: On !CONFIG_MEMCG, this will always return NULL; it | |
277 | * would be better if the root_mem_cgroup existed in all | |
278 | * configurations instead. | |
279 | */ | |
280 | memcg = mem_cgroup_from_id(memcgid); | |
1899ad18 JW |
281 | if (!mem_cgroup_disabled() && !memcg) |
282 | goto out; | |
1e6b1085 | 283 | lruvec = mem_cgroup_lruvec(pgdat, memcg); |
23047a96 | 284 | refault = atomic_long_read(&lruvec->inactive_age); |
fd538803 | 285 | active_file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES); |
162453bf JW |
286 | |
287 | /* | |
1899ad18 | 288 | * Calculate the refault distance |
162453bf | 289 | * |
1899ad18 JW |
290 | * The unsigned subtraction here gives an accurate distance |
291 | * across inactive_age overflows in most cases. There is a | |
292 | * special case: usually, shadow entries have a short lifetime | |
293 | * and are either refaulted or reclaimed along with the inode | |
294 | * before they get too old. But it is not impossible for the | |
295 | * inactive_age to lap a shadow entry in the field, which can | |
296 | * then result in a false small refault distance, leading to a | |
297 | * false activation should this old entry actually refault | |
298 | * again. However, earlier kernels used to deactivate | |
299 | * unconditionally with *every* reclaim invocation for the | |
300 | * longest time, so the occasional inappropriate activation | |
301 | * leading to pressure on the active list is not a problem. | |
162453bf JW |
302 | */ |
303 | refault_distance = (refault - eviction) & EVICTION_MASK; | |
304 | ||
00f3ca2c | 305 | inc_lruvec_state(lruvec, WORKINGSET_REFAULT); |
a528910e | 306 | |
1899ad18 JW |
307 | /* |
308 | * Compare the distance to the existing workingset size. We | |
309 | * don't act on pages that couldn't stay resident even if all | |
310 | * the memory was available to the page cache. | |
311 | */ | |
312 | if (refault_distance > active_file) | |
313 | goto out; | |
314 | ||
315 | SetPageActive(page); | |
316 | atomic_long_inc(&lruvec->inactive_age); | |
317 | inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE); | |
318 | ||
319 | /* Page was active prior to eviction */ | |
320 | if (workingset) { | |
321 | SetPageWorkingset(page); | |
322 | inc_lruvec_state(lruvec, WORKINGSET_RESTORE); | |
a528910e | 323 | } |
1899ad18 | 324 | out: |
2a2e4885 | 325 | rcu_read_unlock(); |
a528910e JW |
326 | } |
327 | ||
328 | /** | |
329 | * workingset_activation - note a page activation | |
330 | * @page: page that is being activated | |
331 | */ | |
332 | void workingset_activation(struct page *page) | |
333 | { | |
55779ec7 | 334 | struct mem_cgroup *memcg; |
23047a96 JW |
335 | struct lruvec *lruvec; |
336 | ||
55779ec7 | 337 | rcu_read_lock(); |
23047a96 JW |
338 | /* |
339 | * Filter non-memcg pages here, e.g. unmap can call | |
340 | * mark_page_accessed() on VDSO pages. | |
341 | * | |
342 | * XXX: See workingset_refault() - this should return | |
343 | * root_mem_cgroup even for !CONFIG_MEMCG. | |
344 | */ | |
55779ec7 JW |
345 | memcg = page_memcg_rcu(page); |
346 | if (!mem_cgroup_disabled() && !memcg) | |
23047a96 | 347 | goto out; |
ef8f2327 | 348 | lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg); |
23047a96 JW |
349 | atomic_long_inc(&lruvec->inactive_age); |
350 | out: | |
55779ec7 | 351 | rcu_read_unlock(); |
a528910e | 352 | } |
449dd698 JW |
353 | |
354 | /* | |
355 | * Shadow entries reflect the share of the working set that does not | |
356 | * fit into memory, so their number depends on the access pattern of | |
357 | * the workload. In most cases, they will refault or get reclaimed | |
358 | * along with the inode, but a (malicious) workload that streams | |
359 | * through files with a total size several times that of available | |
360 | * memory, while preventing the inodes from being reclaimed, can | |
361 | * create excessive amounts of shadow nodes. To keep a lid on this, | |
362 | * track shadow nodes and reclaim them when they grow way past the | |
363 | * point where they would still be useful. | |
364 | */ | |
365 | ||
14b46879 JW |
366 | static struct list_lru shadow_nodes; |
367 | ||
a97e7904 | 368 | void workingset_update_node(struct xa_node *node) |
14b46879 | 369 | { |
14b46879 JW |
370 | /* |
371 | * Track non-empty nodes that contain only shadow entries; | |
372 | * unlink those that contain pages or are being freed. | |
373 | * | |
374 | * Avoid acquiring the list_lru lock when the nodes are | |
375 | * already where they should be. The list_empty() test is safe | |
b93b0163 | 376 | * as node->private_list is protected by the i_pages lock. |
14b46879 | 377 | */ |
68d48e6a JW |
378 | VM_WARN_ON_ONCE(!irqs_disabled()); /* For __inc_lruvec_page_state */ |
379 | ||
01959dfe | 380 | if (node->count && node->count == node->nr_values) { |
68d48e6a | 381 | if (list_empty(&node->private_list)) { |
14b46879 | 382 | list_lru_add(&shadow_nodes, &node->private_list); |
ec9f0238 | 383 | __inc_lruvec_slab_state(node, WORKINGSET_NODES); |
68d48e6a | 384 | } |
14b46879 | 385 | } else { |
68d48e6a | 386 | if (!list_empty(&node->private_list)) { |
14b46879 | 387 | list_lru_del(&shadow_nodes, &node->private_list); |
ec9f0238 | 388 | __dec_lruvec_slab_state(node, WORKINGSET_NODES); |
68d48e6a | 389 | } |
14b46879 JW |
390 | } |
391 | } | |
449dd698 JW |
392 | |
393 | static unsigned long count_shadow_nodes(struct shrinker *shrinker, | |
394 | struct shrink_control *sc) | |
395 | { | |
449dd698 | 396 | unsigned long max_nodes; |
14b46879 | 397 | unsigned long nodes; |
95f9ab2d | 398 | unsigned long pages; |
449dd698 | 399 | |
14b46879 | 400 | nodes = list_lru_shrink_count(&shadow_nodes, sc); |
449dd698 | 401 | |
449dd698 | 402 | /* |
a97e7904 | 403 | * Approximate a reasonable limit for the nodes |
b5388998 JW |
404 | * containing shadow entries. We don't need to keep more |
405 | * shadow entries than possible pages on the active list, | |
406 | * since refault distances bigger than that are dismissed. | |
407 | * | |
408 | * The size of the active list converges toward 100% of | |
409 | * overall page cache as memory grows, with only a tiny | |
410 | * inactive list. Assume the total cache size for that. | |
411 | * | |
412 | * Nodes might be sparsely populated, with only one shadow | |
413 | * entry in the extreme case. Obviously, we cannot keep one | |
414 | * node for every eligible shadow entry, so compromise on a | |
415 | * worst-case density of 1/8th. Below that, not all eligible | |
416 | * refaults can be detected anymore. | |
449dd698 | 417 | * |
a97e7904 | 418 | * On 64-bit with 7 xa_nodes per page and 64 slots |
449dd698 | 419 | * each, this will reclaim shadow entries when they consume |
b5388998 | 420 | * ~1.8% of available memory: |
449dd698 | 421 | * |
a97e7904 | 422 | * PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE |
449dd698 | 423 | */ |
95f9ab2d | 424 | #ifdef CONFIG_MEMCG |
b5388998 | 425 | if (sc->memcg) { |
95f9ab2d | 426 | struct lruvec *lruvec; |
2b487e59 | 427 | int i; |
95f9ab2d | 428 | |
95f9ab2d | 429 | lruvec = mem_cgroup_lruvec(NODE_DATA(sc->nid), sc->memcg); |
2b487e59 | 430 | for (pages = 0, i = 0; i < NR_LRU_LISTS; i++) |
205b20cc JW |
431 | pages += lruvec_page_state_local(lruvec, |
432 | NR_LRU_BASE + i); | |
433 | pages += lruvec_page_state_local(lruvec, NR_SLAB_RECLAIMABLE); | |
434 | pages += lruvec_page_state_local(lruvec, NR_SLAB_UNRECLAIMABLE); | |
95f9ab2d JW |
435 | } else |
436 | #endif | |
437 | pages = node_present_pages(sc->nid); | |
438 | ||
dad4f140 | 439 | max_nodes = pages >> (XA_CHUNK_SHIFT - 3); |
449dd698 | 440 | |
9b996468 KT |
441 | if (!nodes) |
442 | return SHRINK_EMPTY; | |
443 | ||
14b46879 | 444 | if (nodes <= max_nodes) |
449dd698 | 445 | return 0; |
14b46879 | 446 | return nodes - max_nodes; |
449dd698 JW |
447 | } |
448 | ||
449 | static enum lru_status shadow_lru_isolate(struct list_head *item, | |
3f97b163 | 450 | struct list_lru_one *lru, |
449dd698 | 451 | spinlock_t *lru_lock, |
a97e7904 | 452 | void *arg) __must_hold(lru_lock) |
449dd698 | 453 | { |
a97e7904 MW |
454 | struct xa_node *node = container_of(item, struct xa_node, private_list); |
455 | XA_STATE(xas, node->array, 0); | |
449dd698 | 456 | struct address_space *mapping; |
449dd698 JW |
457 | int ret; |
458 | ||
459 | /* | |
460 | * Page cache insertions and deletions synchroneously maintain | |
b93b0163 | 461 | * the shadow node LRU under the i_pages lock and the |
449dd698 JW |
462 | * lru_lock. Because the page cache tree is emptied before |
463 | * the inode can be destroyed, holding the lru_lock pins any | |
a97e7904 | 464 | * address_space that has nodes on the LRU. |
449dd698 | 465 | * |
b93b0163 | 466 | * We can then safely transition to the i_pages lock to |
449dd698 JW |
467 | * pin only the address_space of the particular node we want |
468 | * to reclaim, take the node off-LRU, and drop the lru_lock. | |
469 | */ | |
470 | ||
01959dfe | 471 | mapping = container_of(node->array, struct address_space, i_pages); |
449dd698 JW |
472 | |
473 | /* Coming from the list, invert the lock order */ | |
b93b0163 | 474 | if (!xa_trylock(&mapping->i_pages)) { |
6ca342d0 | 475 | spin_unlock_irq(lru_lock); |
449dd698 JW |
476 | ret = LRU_RETRY; |
477 | goto out; | |
478 | } | |
479 | ||
3f97b163 | 480 | list_lru_isolate(lru, item); |
ec9f0238 | 481 | __dec_lruvec_slab_state(node, WORKINGSET_NODES); |
68d48e6a | 482 | |
449dd698 JW |
483 | spin_unlock(lru_lock); |
484 | ||
485 | /* | |
486 | * The nodes should only contain one or more shadow entries, | |
487 | * no pages, so we expect to be able to remove them all and | |
488 | * delete and free the empty node afterwards. | |
489 | */ | |
01959dfe | 490 | if (WARN_ON_ONCE(!node->nr_values)) |
b936887e | 491 | goto out_invalid; |
01959dfe | 492 | if (WARN_ON_ONCE(node->count != node->nr_values)) |
b936887e | 493 | goto out_invalid; |
a97e7904 MW |
494 | mapping->nrexceptional -= node->nr_values; |
495 | xas.xa_node = xa_parent_locked(&mapping->i_pages, node); | |
496 | xas.xa_offset = node->offset; | |
497 | xas.xa_shift = node->shift + XA_CHUNK_SHIFT; | |
498 | xas_set_update(&xas, workingset_update_node); | |
499 | /* | |
500 | * We could store a shadow entry here which was the minimum of the | |
501 | * shadow entries we were tracking ... | |
502 | */ | |
503 | xas_store(&xas, NULL); | |
ec9f0238 | 504 | __inc_lruvec_slab_state(node, WORKINGSET_NODERECLAIM); |
449dd698 | 505 | |
b936887e | 506 | out_invalid: |
6ca342d0 | 507 | xa_unlock_irq(&mapping->i_pages); |
449dd698 JW |
508 | ret = LRU_REMOVED_RETRY; |
509 | out: | |
449dd698 | 510 | cond_resched(); |
6ca342d0 | 511 | spin_lock_irq(lru_lock); |
449dd698 JW |
512 | return ret; |
513 | } | |
514 | ||
515 | static unsigned long scan_shadow_nodes(struct shrinker *shrinker, | |
516 | struct shrink_control *sc) | |
517 | { | |
b93b0163 | 518 | /* list_lru lock nests inside the IRQ-safe i_pages lock */ |
6b51e881 SAS |
519 | return list_lru_shrink_walk_irq(&shadow_nodes, sc, shadow_lru_isolate, |
520 | NULL); | |
449dd698 JW |
521 | } |
522 | ||
523 | static struct shrinker workingset_shadow_shrinker = { | |
524 | .count_objects = count_shadow_nodes, | |
525 | .scan_objects = scan_shadow_nodes, | |
4b85afbd | 526 | .seeks = 0, /* ->count reports only fully expendable nodes */ |
0a6b76dd | 527 | .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, |
449dd698 JW |
528 | }; |
529 | ||
530 | /* | |
531 | * Our list_lru->lock is IRQ-safe as it nests inside the IRQ-safe | |
b93b0163 | 532 | * i_pages lock. |
449dd698 JW |
533 | */ |
534 | static struct lock_class_key shadow_nodes_key; | |
535 | ||
536 | static int __init workingset_init(void) | |
537 | { | |
612e4493 JW |
538 | unsigned int timestamp_bits; |
539 | unsigned int max_order; | |
449dd698 JW |
540 | int ret; |
541 | ||
612e4493 JW |
542 | BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT); |
543 | /* | |
544 | * Calculate the eviction bucket size to cover the longest | |
545 | * actionable refault distance, which is currently half of | |
546 | * memory (totalram_pages/2). However, memory hotplug may add | |
547 | * some more pages at runtime, so keep working with up to | |
548 | * double the initial memory by using totalram_pages as-is. | |
549 | */ | |
550 | timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT; | |
ca79b0c2 | 551 | max_order = fls_long(totalram_pages() - 1); |
612e4493 JW |
552 | if (max_order > timestamp_bits) |
553 | bucket_order = max_order - timestamp_bits; | |
d3d36c4b | 554 | pr_info("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n", |
612e4493 JW |
555 | timestamp_bits, max_order, bucket_order); |
556 | ||
39887653 | 557 | ret = prealloc_shrinker(&workingset_shadow_shrinker); |
449dd698 JW |
558 | if (ret) |
559 | goto err; | |
c92e8e10 KT |
560 | ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key, |
561 | &workingset_shadow_shrinker); | |
449dd698 JW |
562 | if (ret) |
563 | goto err_list_lru; | |
39887653 | 564 | register_shrinker_prepared(&workingset_shadow_shrinker); |
449dd698 JW |
565 | return 0; |
566 | err_list_lru: | |
39887653 | 567 | free_prealloced_shrinker(&workingset_shadow_shrinker); |
449dd698 JW |
568 | err: |
569 | return ret; | |
570 | } | |
571 | module_init(workingset_init); |