123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750 |
- // SPDX-License-Identifier: GPL-2.0
- /*
- * Workingset detection
- *
- * Copyright (C) 2013 Red Hat, Inc., Johannes Weiner
- */
- #include <linux/memcontrol.h>
- #include <linux/mm_inline.h>
- #include <linux/writeback.h>
- #include <linux/shmem_fs.h>
- #include <linux/pagemap.h>
- #include <linux/atomic.h>
- #include <linux/module.h>
- #include <linux/swap.h>
- #include <linux/dax.h>
- #include <linux/fs.h>
- #include <linux/mm.h>
- /*
- * Double CLOCK lists
- *
- * Per node, two clock lists are maintained for file pages: the
- * inactive and the active list. Freshly faulted pages start out at
- * the head of the inactive list and page reclaim scans pages from the
- * tail. Pages that are accessed multiple times on the inactive list
- * are promoted to the active list, to protect them from reclaim,
- * whereas active pages are demoted to the inactive list when the
- * active list grows too big.
- *
- * fault ------------------------+
- * |
- * +--------------+ | +-------------+
- * reclaim <- | inactive | <-+-- demotion | active | <--+
- * +--------------+ +-------------+ |
- * | |
- * +-------------- promotion ------------------+
- *
- *
- * Access frequency and refault distance
- *
- * A workload is thrashing when its pages are frequently used but they
- * are evicted from the inactive list every time before another access
- * would have promoted them to the active list.
- *
- * In cases where the average access distance between thrashing pages
- * is bigger than the size of memory there is nothing that can be
- * done - the thrashing set could never fit into memory under any
- * circumstance.
- *
- * However, the average access distance could be bigger than the
- * inactive list, yet smaller than the size of memory. In this case,
- * the set could fit into memory if it weren't for the currently
- * active pages - which may be used more, hopefully less frequently:
- *
- * +-memory available to cache-+
- * | |
- * +-inactive------+-active----+
- * a b | c d e f g h i | J K L M N |
- * +---------------+-----------+
- *
- * It is prohibitively expensive to accurately track access frequency
- * of pages. But a reasonable approximation can be made to measure
- * thrashing on the inactive list, after which refaulting pages can be
- * activated optimistically to compete with the existing active pages.
- *
- * Approximating inactive page access frequency - Observations:
- *
- * 1. When a page is accessed for the first time, it is added to the
- * head of the inactive list, slides every existing inactive page
- * towards the tail by one slot, and pushes the current tail page
- * out of memory.
- *
- * 2. When a page is accessed for the second time, it is promoted to
- * the active list, shrinking the inactive list by one slot. This
- * also slides all inactive pages that were faulted into the cache
- * more recently than the activated page towards the tail of the
- * inactive list.
- *
- * Thus:
- *
- * 1. The sum of evictions and activations between any two points in
- * time indicate the minimum number of inactive pages accessed in
- * between.
- *
- * 2. Moving one inactive page N page slots towards the tail of the
- * list requires at least N inactive page accesses.
- *
- * Combining these:
- *
- * 1. When a page is finally evicted from memory, the number of
- * inactive pages accessed while the page was in cache is at least
- * the number of page slots on the inactive list.
- *
- * 2. In addition, measuring the sum of evictions and activations (E)
- * at the time of a page's eviction, and comparing it to another
- * reading (R) at the time the page faults back into memory tells
- * the minimum number of accesses while the page was not cached.
- * This is called the refault distance.
- *
- * Because the first access of the page was the fault and the second
- * access the refault, we combine the in-cache distance with the
- * out-of-cache distance to get the complete minimum access distance
- * of this page:
- *
- * NR_inactive + (R - E)
- *
- * And knowing the minimum access distance of a page, we can easily
- * tell if the page would be able to stay in cache assuming all page
- * slots in the cache were available:
- *
- * NR_inactive + (R - E) <= NR_inactive + NR_active
- *
- * which can be further simplified to
- *
- * (R - E) <= NR_active
- *
- * Put into words, the refault distance (out-of-cache) can be seen as
- * a deficit in inactive list space (in-cache). If the inactive list
- * had (R - E) more page slots, the page would not have been evicted
- * in between accesses, but activated instead. And on a full system,
- * the only thing eating into inactive list space is active pages.
- *
- *
- * Refaulting inactive pages
- *
- * All that is known about the active list is that the pages have been
- * accessed more than once in the past. This means that at any given
- * time there is actually a good chance that pages on the active list
- * are no longer in active use.
- *
- * So when a refault distance of (R - E) is observed and there are at
- * least (R - E) active pages, the refaulting page is activated
- * optimistically in the hope that (R - E) active pages are actually
- * used less frequently than the refaulting page - or even not used at
- * all anymore.
- *
- * That means if inactive cache is refaulting with a suitable refault
- * distance, we assume the cache workingset is transitioning and put
- * pressure on the current active list.
- *
- * If this is wrong and demotion kicks in, the pages which are truly
- * used more frequently will be reactivated while the less frequently
- * used once will be evicted from memory.
- *
- * But if this is right, the stale pages will be pushed out of memory
- * and the used pages get to stay in cache.
- *
- * Refaulting active pages
- *
- * If on the other hand the refaulting pages have recently been
- * deactivated, it means that the active list is no longer protecting
- * actively used cache from reclaim. The cache is NOT transitioning to
- * a different workingset; the existing workingset is thrashing in the
- * space allocated to the page cache.
- *
- *
- * Implementation
- *
- * For each node's LRU lists, a counter for inactive evictions and
- * activations is maintained (node->nonresident_age).
- *
- * On eviction, a snapshot of this counter (along with some bits to
- * identify the node) is stored in the now empty page cache
- * slot of the evicted page. This is called a shadow entry.
- *
- * On cache misses for which there are shadow entries, an eligible
- * refault distance will immediately activate the refaulting page.
- */
- #define WORKINGSET_SHIFT 1
- #define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \
- WORKINGSET_SHIFT + NODES_SHIFT + \
- MEM_CGROUP_ID_SHIFT)
- #define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
- /*
- * Eviction timestamps need to be able to cover the full range of
- * actionable refaults. However, bits are tight in the xarray
- * entry, and after storing the identifier for the lruvec there might
- * not be enough left to represent every single actionable refault. In
- * that case, we have to sacrifice granularity for distance, and group
- * evictions into coarser buckets by shaving off lower timestamp bits.
- */
- static unsigned int bucket_order __read_mostly;
- static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction,
- bool workingset)
- {
- eviction &= EVICTION_MASK;
- eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
- eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
- eviction = (eviction << WORKINGSET_SHIFT) | workingset;
- return xa_mk_value(eviction);
- }
- static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
- unsigned long *evictionp, bool *workingsetp)
- {
- unsigned long entry = xa_to_value(shadow);
- int memcgid, nid;
- bool workingset;
- workingset = entry & ((1UL << WORKINGSET_SHIFT) - 1);
- entry >>= WORKINGSET_SHIFT;
- nid = entry & ((1UL << NODES_SHIFT) - 1);
- entry >>= NODES_SHIFT;
- memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
- entry >>= MEM_CGROUP_ID_SHIFT;
- *memcgidp = memcgid;
- *pgdat = NODE_DATA(nid);
- *evictionp = entry;
- *workingsetp = workingset;
- }
- #ifdef CONFIG_LRU_GEN
- static void *lru_gen_eviction(struct folio *folio)
- {
- int hist;
- unsigned long token;
- unsigned long min_seq;
- struct lruvec *lruvec;
- struct lru_gen_folio *lrugen;
- int type = folio_is_file_lru(folio);
- int delta = folio_nr_pages(folio);
- int refs = folio_lru_refs(folio);
- int tier = lru_tier_from_refs(refs);
- struct mem_cgroup *memcg = folio_memcg(folio);
- struct pglist_data *pgdat = folio_pgdat(folio);
- BUILD_BUG_ON(LRU_GEN_WIDTH + LRU_REFS_WIDTH > BITS_PER_LONG - EVICTION_SHIFT);
- lruvec = mem_cgroup_lruvec(memcg, pgdat);
- lrugen = &lruvec->lrugen;
- min_seq = READ_ONCE(lrugen->min_seq[type]);
- token = (min_seq << LRU_REFS_WIDTH) | max(refs - 1, 0);
- hist = lru_hist_from_seq(min_seq);
- atomic_long_add(delta, &lrugen->evicted[hist][type][tier]);
- return pack_shadow(mem_cgroup_id(memcg), pgdat, token, refs);
- }
- static void lru_gen_refault(struct folio *folio, void *shadow)
- {
- int hist, tier, refs;
- int memcg_id;
- bool workingset;
- unsigned long token;
- unsigned long min_seq;
- struct lruvec *lruvec;
- struct lru_gen_folio *lrugen;
- struct mem_cgroup *memcg;
- struct pglist_data *pgdat;
- int type = folio_is_file_lru(folio);
- int delta = folio_nr_pages(folio);
- unpack_shadow(shadow, &memcg_id, &pgdat, &token, &workingset);
- if (pgdat != folio_pgdat(folio))
- return;
- rcu_read_lock();
- memcg = folio_memcg_rcu(folio);
- if (memcg_id != mem_cgroup_id(memcg))
- goto unlock;
- lruvec = mem_cgroup_lruvec(memcg, pgdat);
- lrugen = &lruvec->lrugen;
- mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta);
- min_seq = READ_ONCE(lrugen->min_seq[type]);
- if ((token >> LRU_REFS_WIDTH) != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)))
- goto unlock;
- hist = lru_hist_from_seq(min_seq);
- /* see the comment in folio_lru_refs() */
- refs = (token & (BIT(LRU_REFS_WIDTH) - 1)) + workingset;
- tier = lru_tier_from_refs(refs);
- atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]);
- mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
- /*
- * Count the following two cases as stalls:
- * 1. For pages accessed through page tables, hotter pages pushed out
- * hot pages which refaulted immediately.
- * 2. For pages accessed multiple times through file descriptors,
- * numbers of accesses might have been out of the range.
- */
- if (lru_gen_in_fault() || refs == BIT(LRU_REFS_WIDTH)) {
- folio_set_workingset(folio);
- mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + type, delta);
- }
- unlock:
- rcu_read_unlock();
- }
- #else /* !CONFIG_LRU_GEN */
- static void *lru_gen_eviction(struct folio *folio)
- {
- return NULL;
- }
- static void lru_gen_refault(struct folio *folio, void *shadow)
- {
- }
- #endif /* CONFIG_LRU_GEN */
- /**
- * workingset_age_nonresident - age non-resident entries as LRU ages
- * @lruvec: the lruvec that was aged
- * @nr_pages: the number of pages to count
- *
- * As in-memory pages are aged, non-resident pages need to be aged as
- * well, in order for the refault distances later on to be comparable
- * to the in-memory dimensions. This function allows reclaim and LRU
- * operations to drive the non-resident aging along in parallel.
- */
- void workingset_age_nonresident(struct lruvec *lruvec, unsigned long nr_pages)
- {
- /*
- * Reclaiming a cgroup means reclaiming all its children in a
- * round-robin fashion. That means that each cgroup has an LRU
- * order that is composed of the LRU orders of its child
- * cgroups; and every page has an LRU position not just in the
- * cgroup that owns it, but in all of that group's ancestors.
- *
- * So when the physical inactive list of a leaf cgroup ages,
- * the virtual inactive lists of all its parents, including
- * the root cgroup's, age as well.
- */
- do {
- atomic_long_add(nr_pages, &lruvec->nonresident_age);
- } while ((lruvec = parent_lruvec(lruvec)));
- }
- /**
- * workingset_eviction - note the eviction of a folio from memory
- * @target_memcg: the cgroup that is causing the reclaim
- * @folio: the folio being evicted
- *
- * Return: a shadow entry to be stored in @folio->mapping->i_pages in place
- * of the evicted @folio so that a later refault can be detected.
- */
- void *workingset_eviction(struct folio *folio, struct mem_cgroup *target_memcg)
- {
- struct pglist_data *pgdat = folio_pgdat(folio);
- unsigned long eviction;
- struct lruvec *lruvec;
- int memcgid;
- /* Folio is fully exclusive and pins folio's memory cgroup pointer */
- VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
- VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
- VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
- if (lru_gen_enabled())
- return lru_gen_eviction(folio);
- lruvec = mem_cgroup_lruvec(target_memcg, pgdat);
- /* XXX: target_memcg can be NULL, go through lruvec */
- memcgid = mem_cgroup_id(lruvec_memcg(lruvec));
- eviction = atomic_long_read(&lruvec->nonresident_age);
- eviction >>= bucket_order;
- workingset_age_nonresident(lruvec, folio_nr_pages(folio));
- return pack_shadow(memcgid, pgdat, eviction,
- folio_test_workingset(folio));
- }
- /**
- * workingset_refault - Evaluate the refault of a previously evicted folio.
- * @folio: The freshly allocated replacement folio.
- * @shadow: Shadow entry of the evicted folio.
- *
- * Calculates and evaluates the refault distance of the previously
- * evicted folio in the context of the node and the memcg whose memory
- * pressure caused the eviction.
- */
- void workingset_refault(struct folio *folio, void *shadow)
- {
- bool file = folio_is_file_lru(folio);
- struct mem_cgroup *eviction_memcg;
- struct lruvec *eviction_lruvec;
- unsigned long refault_distance;
- unsigned long workingset_size;
- struct pglist_data *pgdat;
- struct mem_cgroup *memcg;
- unsigned long eviction;
- struct lruvec *lruvec;
- unsigned long refault;
- bool workingset;
- int memcgid;
- long nr;
- if (lru_gen_enabled()) {
- lru_gen_refault(folio, shadow);
- return;
- }
- unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset);
- eviction <<= bucket_order;
- rcu_read_lock();
- /*
- * Look up the memcg associated with the stored ID. It might
- * have been deleted since the folio's eviction.
- *
- * Note that in rare events the ID could have been recycled
- * for a new cgroup that refaults a shared folio. This is
- * impossible to tell from the available data. However, this
- * should be a rare and limited disturbance, and activations
- * are always speculative anyway. Ultimately, it's the aging
- * algorithm's job to shake out the minimum access frequency
- * for the active cache.
- *
- * XXX: On !CONFIG_MEMCG, this will always return NULL; it
- * would be better if the root_mem_cgroup existed in all
- * configurations instead.
- */
- eviction_memcg = mem_cgroup_from_id(memcgid);
- if (!mem_cgroup_disabled() && !eviction_memcg)
- goto out;
- eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat);
- refault = atomic_long_read(&eviction_lruvec->nonresident_age);
- /*
- * Calculate the refault distance
- *
- * The unsigned subtraction here gives an accurate distance
- * across nonresident_age overflows in most cases. There is a
- * special case: usually, shadow entries have a short lifetime
- * and are either refaulted or reclaimed along with the inode
- * before they get too old. But it is not impossible for the
- * nonresident_age to lap a shadow entry in the field, which
- * can then result in a false small refault distance, leading
- * to a false activation should this old entry actually
- * refault again. However, earlier kernels used to deactivate
- * unconditionally with *every* reclaim invocation for the
- * longest time, so the occasional inappropriate activation
- * leading to pressure on the active list is not a problem.
- */
- refault_distance = (refault - eviction) & EVICTION_MASK;
- /*
- * The activation decision for this folio is made at the level
- * where the eviction occurred, as that is where the LRU order
- * during folio reclaim is being determined.
- *
- * However, the cgroup that will own the folio is the one that
- * is actually experiencing the refault event.
- */
- nr = folio_nr_pages(folio);
- memcg = folio_memcg(folio);
- lruvec = mem_cgroup_lruvec(memcg, pgdat);
- mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
- mem_cgroup_flush_stats_delayed();
- /*
- * Compare the distance to the existing workingset size. We
- * don't activate pages that couldn't stay resident even if
- * all the memory was available to the workingset. Whether
- * workingset competition needs to consider anon or not depends
- * on having swap.
- */
- workingset_size = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE);
- if (!file) {
- workingset_size += lruvec_page_state(eviction_lruvec,
- NR_INACTIVE_FILE);
- }
- if (mem_cgroup_get_nr_swap_pages(memcg) > 0) {
- workingset_size += lruvec_page_state(eviction_lruvec,
- NR_ACTIVE_ANON);
- if (file) {
- workingset_size += lruvec_page_state(eviction_lruvec,
- NR_INACTIVE_ANON);
- }
- }
- if (refault_distance > workingset_size)
- goto out;
- folio_set_active(folio);
- workingset_age_nonresident(lruvec, nr);
- mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + file, nr);
- /* Folio was active prior to eviction */
- if (workingset) {
- folio_set_workingset(folio);
- /* XXX: Move to lru_cache_add() when it supports new vs putback */
- lru_note_cost_folio(folio);
- mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + file, nr);
- }
- out:
- rcu_read_unlock();
- }
- /**
- * workingset_activation - note a page activation
- * @folio: Folio that is being activated.
- */
- void workingset_activation(struct folio *folio)
- {
- struct mem_cgroup *memcg;
- rcu_read_lock();
- /*
- * Filter non-memcg pages here, e.g. unmap can call
- * mark_page_accessed() on VDSO pages.
- *
- * XXX: See workingset_refault() - this should return
- * root_mem_cgroup even for !CONFIG_MEMCG.
- */
- memcg = folio_memcg_rcu(folio);
- if (!mem_cgroup_disabled() && !memcg)
- goto out;
- workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio));
- out:
- rcu_read_unlock();
- }
- /*
- * Shadow entries reflect the share of the working set that does not
- * fit into memory, so their number depends on the access pattern of
- * the workload. In most cases, they will refault or get reclaimed
- * along with the inode, but a (malicious) workload that streams
- * through files with a total size several times that of available
- * memory, while preventing the inodes from being reclaimed, can
- * create excessive amounts of shadow nodes. To keep a lid on this,
- * track shadow nodes and reclaim them when they grow way past the
- * point where they would still be useful.
- */
- struct list_lru shadow_nodes;
- void workingset_update_node(struct xa_node *node)
- {
- struct address_space *mapping;
- /*
- * Track non-empty nodes that contain only shadow entries;
- * unlink those that contain pages or are being freed.
- *
- * Avoid acquiring the list_lru lock when the nodes are
- * already where they should be. The list_empty() test is safe
- * as node->private_list is protected by the i_pages lock.
- */
- mapping = container_of(node->array, struct address_space, i_pages);
- lockdep_assert_held(&mapping->i_pages.xa_lock);
- if (node->count && node->count == node->nr_values) {
- if (list_empty(&node->private_list)) {
- list_lru_add(&shadow_nodes, &node->private_list);
- __inc_lruvec_kmem_state(node, WORKINGSET_NODES);
- }
- } else {
- if (!list_empty(&node->private_list)) {
- list_lru_del(&shadow_nodes, &node->private_list);
- __dec_lruvec_kmem_state(node, WORKINGSET_NODES);
- }
- }
- }
- static unsigned long count_shadow_nodes(struct shrinker *shrinker,
- struct shrink_control *sc)
- {
- unsigned long max_nodes;
- unsigned long nodes;
- unsigned long pages;
- nodes = list_lru_shrink_count(&shadow_nodes, sc);
- if (!nodes)
- return SHRINK_EMPTY;
- /*
- * Approximate a reasonable limit for the nodes
- * containing shadow entries. We don't need to keep more
- * shadow entries than possible pages on the active list,
- * since refault distances bigger than that are dismissed.
- *
- * The size of the active list converges toward 100% of
- * overall page cache as memory grows, with only a tiny
- * inactive list. Assume the total cache size for that.
- *
- * Nodes might be sparsely populated, with only one shadow
- * entry in the extreme case. Obviously, we cannot keep one
- * node for every eligible shadow entry, so compromise on a
- * worst-case density of 1/8th. Below that, not all eligible
- * refaults can be detected anymore.
- *
- * On 64-bit with 7 xa_nodes per page and 64 slots
- * each, this will reclaim shadow entries when they consume
- * ~1.8% of available memory:
- *
- * PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE
- */
- #ifdef CONFIG_MEMCG
- if (sc->memcg) {
- struct lruvec *lruvec;
- int i;
- lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
- for (pages = 0, i = 0; i < NR_LRU_LISTS; i++)
- pages += lruvec_page_state_local(lruvec,
- NR_LRU_BASE + i);
- pages += lruvec_page_state_local(
- lruvec, NR_SLAB_RECLAIMABLE_B) >> PAGE_SHIFT;
- pages += lruvec_page_state_local(
- lruvec, NR_SLAB_UNRECLAIMABLE_B) >> PAGE_SHIFT;
- } else
- #endif
- pages = node_present_pages(sc->nid);
- max_nodes = pages >> (XA_CHUNK_SHIFT - 3);
- if (nodes <= max_nodes)
- return 0;
- return nodes - max_nodes;
- }
- static enum lru_status shadow_lru_isolate(struct list_head *item,
- struct list_lru_one *lru,
- spinlock_t *lru_lock,
- void *arg) __must_hold(lru_lock)
- {
- struct xa_node *node = container_of(item, struct xa_node, private_list);
- struct address_space *mapping;
- int ret;
- /*
- * Page cache insertions and deletions synchronously maintain
- * the shadow node LRU under the i_pages lock and the
- * lru_lock. Because the page cache tree is emptied before
- * the inode can be destroyed, holding the lru_lock pins any
- * address_space that has nodes on the LRU.
- *
- * We can then safely transition to the i_pages lock to
- * pin only the address_space of the particular node we want
- * to reclaim, take the node off-LRU, and drop the lru_lock.
- */
- mapping = container_of(node->array, struct address_space, i_pages);
- /* Coming from the list, invert the lock order */
- if (!xa_trylock(&mapping->i_pages)) {
- spin_unlock_irq(lru_lock);
- ret = LRU_RETRY;
- goto out;
- }
- if (!spin_trylock(&mapping->host->i_lock)) {
- xa_unlock(&mapping->i_pages);
- spin_unlock_irq(lru_lock);
- ret = LRU_RETRY;
- goto out;
- }
- list_lru_isolate(lru, item);
- __dec_lruvec_kmem_state(node, WORKINGSET_NODES);
- spin_unlock(lru_lock);
- /*
- * The nodes should only contain one or more shadow entries,
- * no pages, so we expect to be able to remove them all and
- * delete and free the empty node afterwards.
- */
- if (WARN_ON_ONCE(!node->nr_values))
- goto out_invalid;
- if (WARN_ON_ONCE(node->count != node->nr_values))
- goto out_invalid;
- xa_delete_node(node, workingset_update_node);
- __inc_lruvec_kmem_state(node, WORKINGSET_NODERECLAIM);
- out_invalid:
- xa_unlock_irq(&mapping->i_pages);
- if (mapping_shrinkable(mapping))
- inode_add_lru(mapping->host);
- spin_unlock(&mapping->host->i_lock);
- ret = LRU_REMOVED_RETRY;
- out:
- cond_resched();
- spin_lock_irq(lru_lock);
- return ret;
- }
- static unsigned long scan_shadow_nodes(struct shrinker *shrinker,
- struct shrink_control *sc)
- {
- /* list_lru lock nests inside the IRQ-safe i_pages lock */
- return list_lru_shrink_walk_irq(&shadow_nodes, sc, shadow_lru_isolate,
- NULL);
- }
- static struct shrinker workingset_shadow_shrinker = {
- .count_objects = count_shadow_nodes,
- .scan_objects = scan_shadow_nodes,
- .seeks = 0, /* ->count reports only fully expendable nodes */
- .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
- };
- /*
- * Our list_lru->lock is IRQ-safe as it nests inside the IRQ-safe
- * i_pages lock.
- */
- static struct lock_class_key shadow_nodes_key;
- static int __init workingset_init(void)
- {
- unsigned int timestamp_bits;
- unsigned int max_order;
- int ret;
- BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT);
- /*
- * Calculate the eviction bucket size to cover the longest
- * actionable refault distance, which is currently half of
- * memory (totalram_pages/2). However, memory hotplug may add
- * some more pages at runtime, so keep working with up to
- * double the initial memory by using totalram_pages as-is.
- */
- timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT;
- max_order = fls_long(totalram_pages() - 1);
- if (max_order > timestamp_bits)
- bucket_order = max_order - timestamp_bits;
- pr_info("workingset: timestamp_bits=%d max_order=%d bucket_order=%u\n",
- timestamp_bits, max_order, bucket_order);
- ret = prealloc_shrinker(&workingset_shadow_shrinker, "mm-shadow");
- if (ret)
- goto err;
- ret = __list_lru_init(&shadow_nodes, true, &shadow_nodes_key,
- &workingset_shadow_shrinker);
- if (ret)
- goto err_list_lru;
- register_shrinker_prepared(&workingset_shadow_shrinker);
- return 0;
- err_list_lru:
- free_prealloced_shrinker(&workingset_shadow_shrinker);
- err:
- return ret;
- }
- module_init(workingset_init);
|