1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Workingset detection
4 *
5 * Copyright (C) 2013 Red Hat, Inc., Johannes Weiner
6 */
7
8 #include <linux/memcontrol.h>
9 #include <linux/mm_inline.h>
10 #include <linux/writeback.h>
11 #include <linux/shmem_fs.h>
12 #include <linux/pagemap.h>
13 #include <linux/atomic.h>
14 #include <linux/module.h>
15 #include <linux/swap.h>
16 #include <linux/dax.h>
17 #include <linux/fs.h>
18 #include <linux/mm.h>
19
20 /*
21 * Double CLOCK lists
22 *
23 * Per node, two clock lists are maintained for file pages: the
24 * inactive and the active list. Freshly faulted pages start out at
25 * the head of the inactive list and page reclaim scans pages from the
26 * tail. Pages that are accessed multiple times on the inactive list
27 * are promoted to the active list, to protect them from reclaim,
28 * whereas active pages are demoted to the inactive list when the
29 * active list grows too big.
30 *
31 * fault ------------------------+
32 * |
33 * +--------------+ | +-------------+
34 * reclaim <- | inactive | <-+-- demotion | active | <--+
35 * +--------------+ +-------------+ |
36 * | |
37 * +-------------- promotion ------------------+
38 *
39 *
40 * Access frequency and refault distance
41 *
42 * A workload is thrashing when its pages are frequently used but they
43 * are evicted from the inactive list every time before another access
44 * would have promoted them to the active list.
45 *
46 * In cases where the average access distance between thrashing pages
47 * is bigger than the size of memory there is nothing that can be
48 * done - the thrashing set could never fit into memory under any
49 * circumstance.
50 *
51 * However, the average access distance could be bigger than the
52 * inactive list, yet smaller than the size of memory. In this case,
53 * the set could fit into memory if it weren't for the currently
54 * active pages - which may be used more, hopefully less frequently:
55 *
56 * +-memory available to cache-+
57 * | |
58 * +-inactive------+-active----+
59 * a b | c d e f g h i | J K L M N |
60 * +---------------+-----------+
61 *
62 * It is prohibitively expensive to accurately track access frequency
63 * of pages. But a reasonable approximation can be made to measure
64 * thrashing on the inactive list, after which refaulting pages can be
65 * activated optimistically to compete with the existing active pages.
66 *
67 * Approximating inactive page access frequency - Observations:
68 *
69 * 1. When a page is accessed for the first time, it is added to the
70 * head of the inactive list, slides every existing inactive page
71 * towards the tail by one slot, and pushes the current tail page
72 * out of memory.
73 *
74 * 2. When a page is accessed for the second time, it is promoted to
75 * the active list, shrinking the inactive list by one slot. This
76 * also slides all inactive pages that were faulted into the cache
77 * more recently than the activated page towards the tail of the
78 * inactive list.
79 *
80 * Thus:
81 *
82 * 1. The sum of evictions and activations between any two points in
83 * time indicate the minimum number of inactive pages accessed in
84 * between.
85 *
86 * 2. Moving one inactive page N page slots towards the tail of the
87 * list requires at least N inactive page accesses.
88 *
89 * Combining these:
90 *
91 * 1. When a page is finally evicted from memory, the number of
92 * inactive pages accessed while the page was in cache is at least
93 * the number of page slots on the inactive list.
94 *
95 * 2. In addition, measuring the sum of evictions and activations (E)
96 * at the time of a page's eviction, and comparing it to another
97 * reading (R) at the time the page faults back into memory tells
98 * the minimum number of accesses while the page was not cached.
99 * This is called the refault distance.
100 *
101 * Because the first access of the page was the fault and the second
102 * access the refault, we combine the in-cache distance with the
103 * out-of-cache distance to get the complete minimum access distance
104 * of this page:
105 *
106 * NR_inactive + (R - E)
107 *
108 * And knowing the minimum access distance of a page, we can easily
109 * tell if the page would be able to stay in cache assuming all page
110 * slots in the cache were available:
111 *
112 * NR_inactive + (R - E) <= NR_inactive + NR_active
113 *
114 * which can be further simplified to
115 *
116 * (R - E) <= NR_active
117 *
118 * Put into words, the refault distance (out-of-cache) can be seen as
119 * a deficit in inactive list space (in-cache). If the inactive list
120 * had (R - E) more page slots, the page would not have been evicted
121 * in between accesses, but activated instead. And on a full system,
122 * the only thing eating into inactive list space is active pages.
123 *
124 *
125 * Refaulting inactive pages
126 *
127 * All that is known about the active list is that the pages have been
128 * accessed more than once in the past. This means that at any given
129 * time there is actually a good chance that pages on the active list
130 * are no longer in active use.
131 *
132 * So when a refault distance of (R - E) is observed and there are at
133 * least (R - E) active pages, the refaulting page is activated
134 * optimistically in the hope that (R - E) active pages are actually
135 * used less frequently than the refaulting page - or even not used at
136 * all anymore.
137 *
138 * That means if inactive cache is refaulting with a suitable refault
139 * distance, we assume the cache workingset is transitioning and put
140 * pressure on the current active list.
141 *
142 * If this is wrong and demotion kicks in, the pages which are truly
143 * used more frequently will be reactivated while the less frequently
144 * used once will be evicted from memory.
145 *
146 * But if this is right, the stale pages will be pushed out of memory
147 * and the used pages get to stay in cache.
148 *
149 * Refaulting active pages
150 *
151 * If on the other hand the refaulting pages have recently been
152 * deactivated, it means that the active list is no longer protecting
153 * actively used cache from reclaim. The cache is NOT transitioning to
154 * a different workingset; the existing workingset is thrashing in the
155 * space allocated to the page cache.
156 *
157 *
158 * Implementation
159 *
160 * For each node's LRU lists, a counter for inactive evictions and
161 * activations is maintained (node->nonresident_age).
162 *
163 * On eviction, a snapshot of this counter (along with some bits to
164 * identify the node) is stored in the now empty page cache
165 * slot of the evicted page. This is called a shadow entry.
166 *
167 * On cache misses for which there are shadow entries, an eligible
168 * refault distance will immediately activate the refaulting page.
169 */
170
171 #define WORKINGSET_SHIFT 1
172 #define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \
173 WORKINGSET_SHIFT + NODES_SHIFT + \
174 MEM_CGROUP_ID_SHIFT)
175 #define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
176
177 /*
178 * Eviction timestamps need to be able to cover the full range of
179 * actionable refaults. However, bits are tight in the xarray
180 * entry, and after storing the identifier for the lruvec there might
181 * not be enough left to represent every single actionable refault. In
182 * that case, we have to sacrifice granularity for distance, and group
183 * evictions into coarser buckets by shaving off lower timestamp bits.
184 */
185 static unsigned int bucket_order __read_mostly;
186
pack_shadow(int memcgid,pg_data_t * pgdat,unsigned long eviction,bool workingset)187 static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction,
188 bool workingset)
189 {
190 eviction >>= bucket_order;
191 eviction &= EVICTION_MASK;
192 eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
193 eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
194 eviction = (eviction << WORKINGSET_SHIFT) | workingset;
195
196 return xa_mk_value(eviction);
197 }
198
unpack_shadow(void * shadow,int * memcgidp,pg_data_t ** pgdat,unsigned long * evictionp,bool * workingsetp)199 static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
200 unsigned long *evictionp, bool *workingsetp)
201 {
202 unsigned long entry = xa_to_value(shadow);
203 int memcgid, nid;
204 bool workingset;
205
206 workingset = entry & ((1UL << WORKINGSET_SHIFT) - 1);
207 entry >>= WORKINGSET_SHIFT;
208 nid = entry & ((1UL << NODES_SHIFT) - 1);
209 entry >>= NODES_SHIFT;
210 memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
211 entry >>= MEM_CGROUP_ID_SHIFT;
212
213 *memcgidp = memcgid;
214 *pgdat = NODE_DATA(nid);
215 *evictionp = entry << bucket_order;
216 *workingsetp = workingset;
217 }
218
219 /**
220 * workingset_age_nonresident - age non-resident entries as LRU ages
221 * @lruvec: the lruvec that was aged
222 * @nr_pages: the number of pages to count
223 *
224 * As in-memory pages are aged, non-resident pages need to be aged as
225 * well, in order for the refault distances later on to be comparable
226 * to the in-memory dimensions. This function allows reclaim and LRU
227 * operations to drive the non-resident aging along in parallel.
228 */
workingset_age_nonresident(struct lruvec * lruvec,unsigned long nr_pages)229 void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages)
230 {
231 /*
232 * Reclaiming a cgroup means reclaiming all its children in a
233 * round-robin fashion. That means that each cgroup has an LRU
234 * order that is composed of the LRU orders of its child
235 * cgroups; and every page has an LRU position not just in the
236 * cgroup that owns it, but in all of that group's ancestors.
237 *
238 * So when the physical inactive list of a leaf cgroup ages,
239 * the virtual inactive lists of all its parents, including
240 * the root cgroup's, age as well.
241 */
242 do {
243 atomic_long_add(nr_pages, &lruvec->nonresident_age);
244 } while ((lruvec = parent_lruvec(lruvec)));
245 }
246
247 /**
248 * workingset_eviction - note the eviction of a page from memory
249 * @target_memcg: the cgroup that is causing the reclaim
250 * @page: the page being evicted
251 *
252 * Return: a shadow entry to be stored in @page->mapping->i_pages in place
253 * of the evicted @page so that a later refault can be detected.
254 */
workingset_eviction(struct page * page,struct mem_cgroup * target_memcg)255 void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg)
256 {
257 struct pglist_data *pgdat = page_pgdat(page);
258 unsigned long eviction;
259 struct lruvec *lruvec;
260 int memcgid;
261
262 /* Page is fully exclusive and pins page's memory cgroup pointer */
263 VM_BUG_ON_PAGE(PageLRU(page), page);
264 VM_BUG_ON_PAGE(page_count(page), page);
265 VM_BUG_ON_PAGE(!PageLocked(page), page);
266
267 lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
268 /* XXX: target_memcg can be NULL, go through lruvec */
269 memcgid = mem_cgroup_id(lruvec_memcg(lruvec));
270 eviction = atomic_long_read(&lruvec->nonresident_age);
271 workingset_age_nonresident(lruvec, thp_nr_pages(page));
272 return pack_shadow(memcgid, pgdat, eviction, PageWorkingset(page));
273 }
274
275 /**
276 * workingset_refault - evaluate the refault of a previously evicted page
277 * @page: the freshly allocated replacement page
278 * @shadow: shadow entry of the evicted page
279 *
280 * Calculates and evaluates the refault distance of the previously
281 * evicted page in the context of the node and the memcg whose memory
282 * pressure caused the eviction.
283 */
workingset_refault(struct page * page,void * shadow)284 void workingset_refault(struct page *page, void *shadow)
285 {
286 bool file = page_is_file_lru(page);
287 struct mem_cgroup *eviction_memcg;
288 struct lruvec *eviction_lruvec;
289 unsigned long refault_distance;
290 unsigned long workingset_size;
291 struct pglist_data *pgdat;
292 struct mem_cgroup *memcg;
293 unsigned long eviction;
294 struct lruvec *lruvec;
295 unsigned long refault;
296 bool workingset;
297 int memcgid;
298
299 unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset);
300
301 rcu_read_lock();
302 /*
303 * Look up the memcg associated with the stored ID. It might
304 * have been deleted since the page's eviction.
305 *
306 * Note that in rare events the ID could have been recycled
307 * for a new cgroup that refaults a shared page. This is
308 * impossible to tell from the available data. However, this
309 * should be a rare and limited disturbance, and activations
310 * are always speculative anyway. Ultimately, it's the aging
311 * algorithm's job to shake out the minimum access frequency
312 * for the active cache.
313 *
314 * XXX: On !CONFIG_MEMCG, this will always return NULL; it
315 * would be better if the root_mem_cgroup existed in all
316 * configurations instead.
317 */
318 eviction_memcg = mem_cgroup_from_id(memcgid);
319 if (!mem_cgroup_disabled() && !eviction_memcg)
320 goto out;
321 eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat);
322 refault = atomic_long_read(&eviction_lruvec->nonresident_age);
323
324 /*
325 * Calculate the refault distance
326 *
327 * The unsigned subtraction here gives an accurate distance
328 * across nonresident_age overflows in most cases. There is a
329 * special case: usually, shadow entries have a short lifetime
330 * and are either refaulted or reclaimed along with the inode
331 * before they get too old. But it is not impossible for the
332 * nonresident_age to lap a shadow entry in the field, which
333 * can then result in a false small refault distance, leading
334 * to a false activation should this old entry actually
335 * refault again. However, earlier kernels used to deactivate
336 * unconditionally with *every* reclaim invocation for the
337 * longest time, so the occasional inappropriate activation
338 * leading to pressure on the active list is not a problem.
339 */
340 refault_distance = (refault - eviction) & EVICTION_MASK;
341
342 /*
343 * The activation decision for this page is made at the level
344 * where the eviction occurred, as that is where the LRU order
345 * during page reclaim is being determined.
346 *
347 * However, the cgroup that will own the page is the one that
348 * is actually experiencing the refault event.
349 */
350 memcg = page_memcg(page);
351 lruvec = mem_cgroup_lruvec(memcg, pgdat);
352
353 inc_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file);
354
355 mem_cgroup_flush_stats();
356 /*
357 * Compare the distance to the existing workingset size. We
358 * don't activate pages that couldn't stay resident even if
359 * all the memory was available to the workingset. Whether
360 * workingset competition needs to consider anon or not depends
361 * on having swap.
362 */
363 workingset_size = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE);
364 if (!file) {
365 workingset_size += lruvec_page_state(eviction_lruvec,
366 NR_INACTIVE_FILE);
367 }
368 if (mem_cgroup_get_nr_swap_pages(memcg) > 0) {
369 workingset_size += lruvec_page_state(eviction_lruvec,
370 NR_ACTIVE_ANON);
371 if (file) {
372 workingset_size += lruvec_page_state(eviction_lruvec,
373 NR_INACTIVE_ANON);
374 }
375 }
376 if (refault_distance > workingset_size)
377 goto out;
378
379 SetPageActive(page);
380 workingset_age_nonresident(lruvec, thp_nr_pages(page));
381 inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + file);
382
383 /* Page was active prior to eviction */
384 if (workingset) {
385 SetPageWorkingset(page);
386 /* XXX: Move to lru_cache_add() when it supports new vs putback */
387 lru_note_cost_page(page);
388 inc_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + file);
389 }
390 out:
391 rcu_read_unlock();
392 }
393
394 /**
395 * workingset_activation - note a page activation
396 * @page: page that is being activated
397 */
workingset_activation(struct page * page)398 void workingset_activation(struct page *page)
399 {
400 struct mem_cgroup *memcg;
401 struct lruvec *lruvec;
402
403 rcu_read_lock();
404 /*
405 * Filter non-memcg pages here, e.g. unmap can call
406 * mark_page_accessed() on VDSO pages.
407 *
408 * XXX: See workingset_refault() - this should return
409 * root_mem_cgroup even for !CONFIG_MEMCG.
410 */
411 memcg = page_memcg_rcu(page);
412 if (!mem_cgroup_disabled() && !memcg)
413 goto out;
414 lruvec = mem_cgroup_page_lruvec(page);
415 workingset_age_nonresident(lruvec, thp_nr_pages(page));
416 out:
417 rcu_read_unlock();
418 }
419
420 /*
421 * Shadow entries reflect the share of the working set that does not
422 * fit into memory, so their number depends on the access pattern of
423 * the workload. In most cases, they will refault or get reclaimed
424 * along with the inode, but a (malicious) workload that streams
425 * through files with a total size several times that of available
426 * memory, while preventing the inodes from being reclaimed, can
427 * create excessive amounts of shadow nodes. To keep a lid on this,
428 * track shadow nodes and reclaim them when they grow way past the
429 * point where they would still be useful.
430 */
431
432 static struct list_lru shadow_nodes;
433
workingset_update_node(struct xa_node * node)434 void workingset_update_node(struct xa_node *node)
435 {
436 /*
437 * Track non-empty nodes that contain only shadow entries;
438 * unlink those that contain pages or are being freed.
439 *
440 * Avoid acquiring the list_lru lock when the nodes are
441 * already where they should be. The list_empty() test is safe
442 * as node->private_list is protected by the i_pages lock.
443 */
444 VM_WARN_ON_ONCE(!irqs_disabled()); /* For __inc_lruvec_page_state */
445
446 if (node->count && node->count == node->nr_values) {
447 if (list_empty(&node->private_list)) {
448 list_lru_add(&shadow_nodes, &node->private_list);
449 __inc_lruvec_kmem_state(node, WORKINGSET_NODES);
450 }
451 } else {
452 if (!list_empty(&node->private_list)) {
453 list_lru_del(&shadow_nodes, &node->private_list);
454 __dec_lruvec_kmem_state(node, WORKINGSET_NODES);
455 }
456 }
457 }
458
count_shadow_nodes(struct shrinker * shrinker,struct shrink_control * sc)459 static unsigned long count_shadow_nodes(struct shrinker *shrinker,
460 struct shrink_control *sc)
461 {
462 unsigned long max_nodes;
463 unsigned long nodes;
464 unsigned long pages;
465
466 nodes = list_lru_shrink_count(&shadow_nodes, sc);
467 if (!nodes)
468 return SHRINK_EMPTY;
469
470 /*
471 * Approximate a reasonable limit for the nodes
472 * containing shadow entries. We don't need to keep more
473 * shadow entries than possible pages on the active list,
474 * since refault distances bigger than that are dismissed.
475 *
476 * The size of the active list converges toward 100% of
477 * overall page cache as memory grows, with only a tiny
478 * inactive list. Assume the total cache size for that.
479 *
480 * Nodes might be sparsely populated, with only one shadow
481 * entry in the extreme case. Obviously, we cannot keep one
482 * node for every eligible shadow entry, so compromise on a
483 * worst-case density of 1/8th. Below that, not all eligible
484 * refaults can be detected anymore.
485 *
486 * On 64-bit with 7 xa_nodes per page and 64 slots
487 * each, this will reclaim shadow entries when they consume
488 * ~1.8% of available memory:
489 *
490 * PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE
491 */
492 #ifdef CONFIG_MEMCG
493 if (sc->memcg) {
494 struct lruvec *lruvec;
495 int i;
496
497 lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
498 for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
499 pages += lruvec_page_state_local(lruvec,
500 NR_LRU_BASE + i);
501 pages += lruvec_page_state_local(
502 lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
503 pages += lruvec_page_state_local(
504 lruvec, NR_SLAB_UNRECLAIMABLE_B) >> PAGE_SHIFT;
505 } else
506 #endif
507 pages = node_present_pages(sc->nid);
508
509 max_nodes = pages >> (XA_CHUNK_SHIFT - 3);
510
511 if (nodes <= max_nodes)
512 return 0;
513 return nodes - max_nodes;
514 }
515
shadow_lru_isolate(struct list_head * item,struct list_lru_one * lru,spinlock_t * lru_lock,void * arg)516 static enum lru_status shadow_lru_isolate(struct list_head *item,
517 struct list_lru_one *lru,
518 spinlock_t *lru_lock,
519 void *arg) __must_hold(lru_lock)
520 {
521 struct xa_node *node = container_of(item, struct xa_node, private_list);
522 struct address_space *mapping;
523 int ret;
524
525 /*
526 * Page cache insertions and deletions synchronously maintain
527 * the shadow node LRU under the i_pages lock and the
528 * lru_lock. Because the page cache tree is emptied before
529 * the inode can be destroyed, holding the lru_lock pins any
530 * address_space that has nodes on the LRU.
531 *
532 * We can then safely transition to the i_pages lock to
533 * pin only the address_space of the particular node we want
534 * to reclaim, take the node off-LRU, and drop the lru_lock.
535 */
536
537 mapping = container_of(node->array, struct address_space, i_pages);
538
539 /* Coming from the list, invert the lock order */
540 if (!xa_trylock(&mapping->i_pages)) {
541 spin_unlock_irq(lru_lock);
542 ret = LRU_RETRY;
543 goto out;
544 }
545
546 list_lru_isolate(lru, item);
547 __dec_lruvec_kmem_state(node, WORKINGSET_NODES);
548
549 spin_unlock(lru_lock);
550
551 /*
552 * The nodes should only contain one or more shadow entries,
553 * no pages, so we expect to be able to remove them all and
554 * delete and free the empty node afterwards.
555 */
556 if (WARN_ON_ONCE(!node->nr_values))
557 goto out_invalid;
558 if (WARN_ON_ONCE(node->count != node->nr_values))
559 goto out_invalid;
560 xa_delete_node(node, workingset_update_node);
561 __inc_lruvec_kmem_state(node, WORKINGSET_NODERECLAIM);
562
563 out_invalid:
564 xa_unlock_irq(&mapping->i_pages);
565 ret = LRU_REMOVED_RETRY;
566 out:
567 cond_resched();
568 spin_lock_irq(lru_lock);
569 return ret;
570 }
571
scan_shadow_nodes(struct shrinker * shrinker,struct shrink_control * sc)572 static unsigned long scan_shadow_nodes(struct shrinker *shrinker,
573 struct shrink_control *sc)
574 {
575 /* list_lru lock nests inside the IRQ-safe i_pages lock */
576 return list_lru_shrink_walk_irq(&shadow_nodes, sc, shadow_lru_isolate,
577 NULL);
578 }
579
580 static struct shrinker workingset_shadow_shrinker = {
581 .count_objects = count_shadow_nodes,
582 .scan_objects = scan_shadow_nodes,
583 .seeks = 0, /* ->count reports only fully expendable nodes */
584 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
585 };
586
587 /*
588 * Our list_lru->lock is IRQ-safe as it nests inside the IRQ-safe
589 * i_pages lock.
590 */
591 static struct lock_class_key shadow_nodes_key;
592
workingset_init(void)593 static int __init workingset_init(void)
594 {
595 unsigned int timestamp_bits;
596 unsigned int max_order;
597 int ret;
598
599 BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT);
600 /*
601 * Calculate the eviction bucket size to cover the longest
602 * actionable refault distance, which is currently half of
603 * memory (totalram_pages/2). However, memory hotplug may add
604 * some more pages at runtime, so keep working with up to
605 * double the initial memory by using totalram_pages as-is.
606 */
607 timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT;
608 max_order = fls_long(totalram_pages() - 1);
609 if (max_order > timestamp_bits)
610 bucket_order = max_order - timestamp_bits;
611 pr_info("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n",
612 timestamp_bits, max_order, bucket_order);
613
614 ret = prealloc_shrinker(&workingset_shadow_shrinker);
615 if (ret)
616 goto err;
617 ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key,
618 &workingset_shadow_shrinker);
619 if (ret)
620 goto err_list_lru;
621 register_shrinker_prepared(&workingset_shadow_shrinker);
622 return 0;
623 err_list_lru:
624 free_prealloced_shrinker(&workingset_shadow_shrinker);
625 err:
626 return ret;
627 }
628 module_init(workingset_init);
629
