--- /dev/null
+/*
+ * linux/mm/compaction.c
+ *
+ * Memory compaction for the reduction of external fragmentation. Note that
+ * this heavily depends upon page migration to do all the real heavy
+ * lifting
+ *
+ * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
+ */
+#include <linux/swap.h>
+#include <linux/migrate.h>
+#include <linux/compaction.h>
+#include <linux/mm_inline.h>
+#include <linux/backing-dev.h>
+#include <linux/sysctl.h>
+#include <linux/sysfs.h>
+#include <linux/balloon_compaction.h>
+#include <linux/page-isolation.h>
+#include <linux/kasan.h>
+#include "internal.h"
+
+#ifdef CONFIG_COMPACTION
+static inline void count_compact_event(enum vm_event_item item)
+{
+ count_vm_event(item);
+}
+
+static inline void count_compact_events(enum vm_event_item item, long delta)
+{
+ count_vm_events(item, delta);
+}
+#else
+#define count_compact_event(item) do { } while (0)
+#define count_compact_events(item, delta) do { } while (0)
+#endif
+
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+#ifdef CONFIG_TRACEPOINTS
+static const char *const compaction_status_string[] = {
+ "deferred",
+ "skipped",
+ "continue",
+ "partial",
+ "complete",
+ "no_suitable_page",
+ "not_suitable_zone",
+};
+#endif
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/compaction.h>
+
+static unsigned long release_freepages(struct list_head *freelist)
+{
+ struct page *page, *next;
+ unsigned long high_pfn = 0;
+
+ list_for_each_entry_safe(page, next, freelist, lru) {
+ unsigned long pfn = page_to_pfn(page);
+ list_del(&page->lru);
+ __free_page(page);
+ if (pfn > high_pfn)
+ high_pfn = pfn;
+ }
+
+ return high_pfn;
+}
+
+static void map_pages(struct list_head *list)
+{
+ struct page *page;
+
+ list_for_each_entry(page, list, lru) {
+ arch_alloc_page(page, 0);
+ kernel_map_pages(page, 1, 1);
+ kasan_alloc_pages(page, 0);
+ }
+}
+
+static inline bool migrate_async_suitable(int migratetype)
+{
+ return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
+}
+
+/*
+ * Check that the whole (or subset of) a pageblock given by the interval of
+ * [start_pfn, end_pfn) is valid and within the same zone, before scanning it
+ * with the migration of free compaction scanner. The scanners then need to
+ * use only pfn_valid_within() check for arches that allow holes within
+ * pageblocks.
+ *
+ * Return struct page pointer of start_pfn, or NULL if checks were not passed.
+ *
+ * It's possible on some configurations to have a setup like node0 node1 node0
+ * i.e. it's possible that all pages within a zones range of pages do not
+ * belong to a single zone. We assume that a border between node0 and node1
+ * can occur within a single pageblock, but not a node0 node1 node0
+ * interleaving within a single pageblock. It is therefore sufficient to check
+ * the first and last page of a pageblock and avoid checking each individual
+ * page in a pageblock.
+ */
+static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
+ unsigned long end_pfn, struct zone *zone)
+{
+ struct page *start_page;
+ struct page *end_page;
+
+ /* end_pfn is one past the range we are checking */
+ end_pfn--;
+
+ if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
+ return NULL;
+
+ start_page = pfn_to_page(start_pfn);
+
+ if (page_zone(start_page) != zone)
+ return NULL;
+
+ end_page = pfn_to_page(end_pfn);
+
+ /* This gives a shorter code than deriving page_zone(end_page) */
+ if (page_zone_id(start_page) != page_zone_id(end_page))
+ return NULL;
+
+ return start_page;
+}
+
+#ifdef CONFIG_COMPACTION
+
+/* Do not skip compaction more than 64 times */
+#define COMPACT_MAX_DEFER_SHIFT 6
+
+/*
+ * Compaction is deferred when compaction fails to result in a page
+ * allocation success. 1 << compact_defer_limit compactions are skipped up
+ * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
+ */
+void defer_compaction(struct zone *zone, int order)
+{
+ zone->compact_considered = 0;
+ zone->compact_defer_shift++;
+
+ if (order < zone->compact_order_failed)
+ zone->compact_order_failed = order;
+
+ if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
+ zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
+
+ trace_mm_compaction_defer_compaction(zone, order);
+}
+
+/* Returns true if compaction should be skipped this time */
+bool compaction_deferred(struct zone *zone, int order)
+{
+ unsigned long defer_limit = 1UL << zone->compact_defer_shift;
+
+ if (order < zone->compact_order_failed)
+ return false;
+
+ /* Avoid possible overflow */
+ if (++zone->compact_considered > defer_limit)
+ zone->compact_considered = defer_limit;
+
+ if (zone->compact_considered >= defer_limit)
+ return false;
+
+ trace_mm_compaction_deferred(zone, order);
+
+ return true;
+}
+
+/*
+ * Update defer tracking counters after successful compaction of given order,
+ * which means an allocation either succeeded (alloc_success == true) or is
+ * expected to succeed.
+ */
+void compaction_defer_reset(struct zone *zone, int order,
+ bool alloc_success)
+{
+ if (alloc_success) {
+ zone->compact_considered = 0;
+ zone->compact_defer_shift = 0;
+ }
+ if (order >= zone->compact_order_failed)
+ zone->compact_order_failed = order + 1;
+
+ trace_mm_compaction_defer_reset(zone, order);
+}
+
+/* Returns true if restarting compaction after many failures */
+bool compaction_restarting(struct zone *zone, int order)
+{
+ if (order < zone->compact_order_failed)
+ return false;
+
+ return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
+ zone->compact_considered >= 1UL << zone->compact_defer_shift;
+}
+
+/* Returns true if the pageblock should be scanned for pages to isolate. */
+static inline bool isolation_suitable(struct compact_control *cc,
+ struct page *page)
+{
+ if (cc->ignore_skip_hint)
+ return true;
+
+ return !get_pageblock_skip(page);
+}
+
+/*
+ * This function is called to clear all cached information on pageblocks that
+ * should be skipped for page isolation when the migrate and free page scanner
+ * meet.
+ */
+static void __reset_isolation_suitable(struct zone *zone)
+{
+ unsigned long start_pfn = zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(zone);
+ unsigned long pfn;
+
+ zone->compact_cached_migrate_pfn[0] = start_pfn;
+ zone->compact_cached_migrate_pfn[1] = start_pfn;
+ zone->compact_cached_free_pfn = end_pfn;
+ zone->compact_blockskip_flush = false;
+
+ /* Walk the zone and mark every pageblock as suitable for isolation */
+ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
+ struct page *page;
+
+ cond_resched();
+
+ if (!pfn_valid(pfn))
+ continue;
+
+ page = pfn_to_page(pfn);
+ if (zone != page_zone(page))
+ continue;
+
+ clear_pageblock_skip(page);
+ }
+}
+
+void reset_isolation_suitable(pg_data_t *pgdat)
+{
+ int zoneid;
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+ struct zone *zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ /* Only flush if a full compaction finished recently */
+ if (zone->compact_blockskip_flush)
+ __reset_isolation_suitable(zone);
+ }
+}
+
+/*
+ * If no pages were isolated then mark this pageblock to be skipped in the
+ * future. The information is later cleared by __reset_isolation_suitable().
+ */
+static void update_pageblock_skip(struct compact_control *cc,
+ struct page *page, unsigned long nr_isolated,
+ bool migrate_scanner)
+{
+ struct zone *zone = cc->zone;
+ unsigned long pfn;
+
+ if (cc->ignore_skip_hint)
+ return;
+
+ if (!page)
+ return;
+
+ if (nr_isolated)
+ return;
+
+ set_pageblock_skip(page);
+
+ pfn = page_to_pfn(page);
+
+ /* Update where async and sync compaction should restart */
+ if (migrate_scanner) {
+ if (pfn > zone->compact_cached_migrate_pfn[0])
+ zone->compact_cached_migrate_pfn[0] = pfn;
+ if (cc->mode != MIGRATE_ASYNC &&
+ pfn > zone->compact_cached_migrate_pfn[1])
+ zone->compact_cached_migrate_pfn[1] = pfn;
+ } else {
+ if (pfn < zone->compact_cached_free_pfn)
+ zone->compact_cached_free_pfn = pfn;
+ }
+}
+#else
+static inline bool isolation_suitable(struct compact_control *cc,
+ struct page *page)
+{
+ return true;
+}
+
+static void update_pageblock_skip(struct compact_control *cc,
+ struct page *page, unsigned long nr_isolated,
+ bool migrate_scanner)
+{
+}
+#endif /* CONFIG_COMPACTION */
+
+/*
+ * Compaction requires the taking of some coarse locks that are potentially
+ * very heavily contended. For async compaction, back out if the lock cannot
+ * be taken immediately. For sync compaction, spin on the lock if needed.
+ *
+ * Returns true if the lock is held
+ * Returns false if the lock is not held and compaction should abort
+ */
+static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
+ struct compact_control *cc)
+{
+ if (cc->mode == MIGRATE_ASYNC) {
+ if (!spin_trylock_irqsave(lock, *flags)) {
+ cc->contended = COMPACT_CONTENDED_LOCK;
+ return false;
+ }
+ } else {
+ spin_lock_irqsave(lock, *flags);
+ }
+
+ return true;
+}
+
+/*
+ * Compaction requires the taking of some coarse locks that are potentially
+ * very heavily contended. The lock should be periodically unlocked to avoid
+ * having disabled IRQs for a long time, even when there is nobody waiting on
+ * the lock. It might also be that allowing the IRQs will result in
+ * need_resched() becoming true. If scheduling is needed, async compaction
+ * aborts. Sync compaction schedules.
+ * Either compaction type will also abort if a fatal signal is pending.
+ * In either case if the lock was locked, it is dropped and not regained.
+ *
+ * Returns true if compaction should abort due to fatal signal pending, or
+ * async compaction due to need_resched()
+ * Returns false when compaction can continue (sync compaction might have
+ * scheduled)
+ */
+static bool compact_unlock_should_abort(spinlock_t *lock,
+ unsigned long flags, bool *locked, struct compact_control *cc)
+{
+ if (*locked) {
+ spin_unlock_irqrestore(lock, flags);
+ *locked = false;
+ }
+
+ if (fatal_signal_pending(current)) {
+ cc->contended = COMPACT_CONTENDED_SCHED;
+ return true;
+ }
+
+ if (need_resched()) {
+ if (cc->mode == MIGRATE_ASYNC) {
+ cc->contended = COMPACT_CONTENDED_SCHED;
+ return true;
+ }
+ cond_resched();
+ }
+
+ return false;
+}
+
+/*
+ * Aside from avoiding lock contention, compaction also periodically checks
+ * need_resched() and either schedules in sync compaction or aborts async
+ * compaction. This is similar to what compact_unlock_should_abort() does, but
+ * is used where no lock is concerned.
+ *
+ * Returns false when no scheduling was needed, or sync compaction scheduled.
+ * Returns true when async compaction should abort.
+ */
+static inline bool compact_should_abort(struct compact_control *cc)
+{
+ /* async compaction aborts if contended */
+ if (need_resched()) {
+ if (cc->mode == MIGRATE_ASYNC) {
+ cc->contended = COMPACT_CONTENDED_SCHED;
+ return true;
+ }
+
+ cond_resched();
+ }
+
+ return false;
+}
+
+/*
+ * Isolate free pages onto a private freelist. If @strict is true, will abort
+ * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
+ * (even though it may still end up isolating some pages).
+ */
+static unsigned long isolate_freepages_block(struct compact_control *cc,
+ unsigned long *start_pfn,
+ unsigned long end_pfn,
+ struct list_head *freelist,
+ bool strict)
+{
+ int nr_scanned = 0, total_isolated = 0;
+ struct page *cursor, *valid_page = NULL;
+ unsigned long flags = 0;
+ bool locked = false;
+ unsigned long blockpfn = *start_pfn;
+
+ cursor = pfn_to_page(blockpfn);
+
+ /* Isolate free pages. */
+ for (; blockpfn < end_pfn; blockpfn++, cursor++) {
+ int isolated, i;
+ struct page *page = cursor;
+
+ /*
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort if fatal signal
+ * pending or async compaction detects need_resched()
+ */
+ if (!(blockpfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(&cc->zone->lock, flags,
+ &locked, cc))
+ break;
+
+ nr_scanned++;
+ if (!pfn_valid_within(blockpfn))
+ goto isolate_fail;
+
+ if (!valid_page)
+ valid_page = page;
+ if (!PageBuddy(page))
+ goto isolate_fail;
+
+ /*
+ * If we already hold the lock, we can skip some rechecking.
+ * Note that if we hold the lock now, checked_pageblock was
+ * already set in some previous iteration (or strict is true),
+ * so it is correct to skip the suitable migration target
+ * recheck as well.
+ */
+ if (!locked) {
+ /*
+ * The zone lock must be held to isolate freepages.
+ * Unfortunately this is a very coarse lock and can be
+ * heavily contended if there are parallel allocations
+ * or parallel compactions. For async compaction do not
+ * spin on the lock and we acquire the lock as late as
+ * possible.
+ */
+ locked = compact_trylock_irqsave(&cc->zone->lock,
+ &flags, cc);
+ if (!locked)
+ break;
+
+ /* Recheck this is a buddy page under lock */
+ if (!PageBuddy(page))
+ goto isolate_fail;
+ }
+
+ /* Found a free page, break it into order-0 pages */
+ isolated = split_free_page(page);
+ total_isolated += isolated;
+ for (i = 0; i < isolated; i++) {
+ list_add(&page->lru, freelist);
+ page++;
+ }
+
+ /* If a page was split, advance to the end of it */
+ if (isolated) {
+ cc->nr_freepages += isolated;
+ if (!strict &&
+ cc->nr_migratepages <= cc->nr_freepages) {
+ blockpfn += isolated;
+ break;
+ }
+
+ blockpfn += isolated - 1;
+ cursor += isolated - 1;
+ continue;
+ }
+
+isolate_fail:
+ if (strict)
+ break;
+ else
+ continue;
+
+ }
+
+ trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
+ nr_scanned, total_isolated);
+
+ /* Record how far we have got within the block */
+ *start_pfn = blockpfn;
+
+ /*
+ * If strict isolation is requested by CMA then check that all the
+ * pages requested were isolated. If there were any failures, 0 is
+ * returned and CMA will fail.
+ */
+ if (strict && blockpfn < end_pfn)
+ total_isolated = 0;
+
+ if (locked)
+ spin_unlock_irqrestore(&cc->zone->lock, flags);
+
+ /* Update the pageblock-skip if the whole pageblock was scanned */
+ if (blockpfn == end_pfn)
+ update_pageblock_skip(cc, valid_page, total_isolated, false);
+
+ count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
+ if (total_isolated)
+ count_compact_events(COMPACTISOLATED, total_isolated);
+ return total_isolated;
+}
+
+/**
+ * isolate_freepages_range() - isolate free pages.
+ * @start_pfn: The first PFN to start isolating.
+ * @end_pfn: The one-past-last PFN.
+ *
+ * Non-free pages, invalid PFNs, or zone boundaries within the
+ * [start_pfn, end_pfn) range are considered errors, cause function to
+ * undo its actions and return zero.
+ *
+ * Otherwise, function returns one-past-the-last PFN of isolated page
+ * (which may be greater then end_pfn if end fell in a middle of
+ * a free page).
+ */
+unsigned long
+isolate_freepages_range(struct compact_control *cc,
+ unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long isolated, pfn, block_end_pfn;
+ LIST_HEAD(freelist);
+
+ pfn = start_pfn;
+ block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+
+ for (; pfn < end_pfn; pfn += isolated,
+ block_end_pfn += pageblock_nr_pages) {
+ /* Protect pfn from changing by isolate_freepages_block */
+ unsigned long isolate_start_pfn = pfn;
+
+ block_end_pfn = min(block_end_pfn, end_pfn);
+
+ /*
+ * pfn could pass the block_end_pfn if isolated freepage
+ * is more than pageblock order. In this case, we adjust
+ * scanning range to right one.
+ */
+ if (pfn >= block_end_pfn) {
+ block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+ block_end_pfn = min(block_end_pfn, end_pfn);
+ }
+
+ if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+ break;
+
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, &freelist, true);
+
+ /*
+ * In strict mode, isolate_freepages_block() returns 0 if
+ * there are any holes in the block (ie. invalid PFNs or
+ * non-free pages).
+ */
+ if (!isolated)
+ break;
+
+ /*
+ * If we managed to isolate pages, it is always (1 << n) *
+ * pageblock_nr_pages for some non-negative n. (Max order
+ * page may span two pageblocks).
+ */
+ }
+
+ /* split_free_page does not map the pages */
+ map_pages(&freelist);
+
+ if (pfn < end_pfn) {
+ /* Loop terminated early, cleanup. */
+ release_freepages(&freelist);
+ return 0;
+ }
+
+ /* We don't use freelists for anything. */
+ return pfn;
+}
+
+/* Update the number of anon and file isolated pages in the zone */
+static void acct_isolated(struct zone *zone, struct compact_control *cc)
+{
+ struct page *page;
+ unsigned int count[2] = { 0, };
+
+ if (list_empty(&cc->migratepages))
+ return;
+
+ list_for_each_entry(page, &cc->migratepages, lru)
+ count[!!page_is_file_cache(page)]++;
+
+ mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
+}
+
+/* Similar to reclaim, but different enough that they don't share logic */
+static bool too_many_isolated(struct zone *zone)
+{
+ unsigned long active, inactive, isolated;
+
+ inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
+ zone_page_state(zone, NR_INACTIVE_ANON);
+ active = zone_page_state(zone, NR_ACTIVE_FILE) +
+ zone_page_state(zone, NR_ACTIVE_ANON);
+ isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
+ zone_page_state(zone, NR_ISOLATED_ANON);
+
+ return isolated > (inactive + active) / 2;
+}
+
+/**
+ * isolate_migratepages_block() - isolate all migrate-able pages within
+ * a single pageblock
+ * @cc: Compaction control structure.
+ * @low_pfn: The first PFN to isolate
+ * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
+ * @isolate_mode: Isolation mode to be used.
+ *
+ * Isolate all pages that can be migrated from the range specified by
+ * [low_pfn, end_pfn). The range is expected to be within same pageblock.
+ * Returns zero if there is a fatal signal pending, otherwise PFN of the
+ * first page that was not scanned (which may be both less, equal to or more
+ * than end_pfn).
+ *
+ * The pages are isolated on cc->migratepages list (not required to be empty),
+ * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
+ * is neither read nor updated.
+ */
+static unsigned long
+isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
+ unsigned long end_pfn, isolate_mode_t isolate_mode)
+{
+ struct zone *zone = cc->zone;
+ unsigned long nr_scanned = 0, nr_isolated = 0;
+ struct list_head *migratelist = &cc->migratepages;
+ struct lruvec *lruvec;
+ unsigned long flags = 0;
+ bool locked = false;
+ struct page *page = NULL, *valid_page = NULL;
+ unsigned long start_pfn = low_pfn;
+
+ /*
+ * Ensure that there are not too many pages isolated from the LRU
+ * list by either parallel reclaimers or compaction. If there are,
+ * delay for some time until fewer pages are isolated
+ */
+ while (unlikely(too_many_isolated(zone))) {
+ /* async migration should just abort */
+ if (cc->mode == MIGRATE_ASYNC)
+ return 0;
+
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+ if (fatal_signal_pending(current))
+ return 0;
+ }
+
+ if (compact_should_abort(cc))
+ return 0;
+
+ /* Time to isolate some pages for migration */
+ for (; low_pfn < end_pfn; low_pfn++) {
+ /*
+ * Periodically drop the lock (if held) regardless of its
+ * contention, to give chance to IRQs. Abort async compaction
+ * if contended.
+ */
+ if (!(low_pfn % SWAP_CLUSTER_MAX)
+ && compact_unlock_should_abort(&zone->lru_lock, flags,
+ &locked, cc))
+ break;
+
+ if (!pfn_valid_within(low_pfn))
+ continue;
+ nr_scanned++;
+
+ page = pfn_to_page(low_pfn);
+
+ if (!valid_page)
+ valid_page = page;
+
+ /*
+ * Skip if free. We read page order here without zone lock
+ * which is generally unsafe, but the race window is small and
+ * the worst thing that can happen is that we skip some
+ * potential isolation targets.
+ */
+ if (PageBuddy(page)) {
+ unsigned long freepage_order = page_order_unsafe(page);
+
+ /*
+ * Without lock, we cannot be sure that what we got is
+ * a valid page order. Consider only values in the
+ * valid order range to prevent low_pfn overflow.
+ */
+ if (freepage_order > 0 && freepage_order < MAX_ORDER)
+ low_pfn += (1UL << freepage_order) - 1;
+ continue;
+ }
+
+ /*
+ * Check may be lockless but that's ok as we recheck later.
+ * It's possible to migrate LRU pages and balloon pages
+ * Skip any other type of page
+ */
+ if (!PageLRU(page)) {
+ if (unlikely(balloon_page_movable(page))) {
+ if (balloon_page_isolate(page)) {
+ /* Successfully isolated */
+ goto isolate_success;
+ }
+ }
+ continue;
+ }
+
+ /*
+ * PageLRU is set. lru_lock normally excludes isolation
+ * splitting and collapsing (collapsing has already happened
+ * if PageLRU is set) but the lock is not necessarily taken
+ * here and it is wasteful to take it just to check transhuge.
+ * Check TransHuge without lock and skip the whole pageblock if
+ * it's either a transhuge or hugetlbfs page, as calling
+ * compound_order() without preventing THP from splitting the
+ * page underneath us may return surprising results.
+ */
+ if (PageTransHuge(page)) {
+ if (!locked)
+ low_pfn = ALIGN(low_pfn + 1,
+ pageblock_nr_pages) - 1;
+ else
+ low_pfn += (1 << compound_order(page)) - 1;
+
+ continue;
+ }
+
+ /*
+ * Migration will fail if an anonymous page is pinned in memory,
+ * so avoid taking lru_lock and isolating it unnecessarily in an
+ * admittedly racy check.
+ */
+ if (!page_mapping(page) &&
+ page_count(page) > page_mapcount(page))
+ continue;
+
+ /* If we already hold the lock, we can skip some rechecking */
+ if (!locked) {
+ locked = compact_trylock_irqsave(&zone->lru_lock,
+ &flags, cc);
+ if (!locked)
+ break;
+
+ /* Recheck PageLRU and PageTransHuge under lock */
+ if (!PageLRU(page))
+ continue;
+ if (PageTransHuge(page)) {
+ low_pfn += (1 << compound_order(page)) - 1;
+ continue;
+ }
+ }
+
+ lruvec = mem_cgroup_page_lruvec(page, zone);
+
+ /* Try isolate the page */
+ if (__isolate_lru_page(page, isolate_mode) != 0)
+ continue;
+
+ VM_BUG_ON_PAGE(PageTransCompound(page), page);
+
+ /* Successfully isolated */
+ del_page_from_lru_list(page, lruvec, page_lru(page));
+
+isolate_success:
+ list_add(&page->lru, migratelist);
+ cc->nr_migratepages++;
+ nr_isolated++;
+
+ /* Avoid isolating too much */
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
+ ++low_pfn;
+ break;
+ }
+ }
+
+ /*
+ * The PageBuddy() check could have potentially brought us outside
+ * the range to be scanned.
+ */
+ if (unlikely(low_pfn > end_pfn))
+ low_pfn = end_pfn;
+
+ if (locked)
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
+
+ /*
+ * Update the pageblock-skip information and cached scanner pfn,
+ * if the whole pageblock was scanned without isolating any page.
+ */
+ if (low_pfn == end_pfn)
+ update_pageblock_skip(cc, valid_page, nr_isolated, true);
+
+ trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
+ nr_scanned, nr_isolated);
+
+ count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
+ if (nr_isolated)
+ count_compact_events(COMPACTISOLATED, nr_isolated);
+
+ return low_pfn;
+}
+
+/**
+ * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
+ * @cc: Compaction control structure.
+ * @start_pfn: The first PFN to start isolating.
+ * @end_pfn: The one-past-last PFN.
+ *
+ * Returns zero if isolation fails fatally due to e.g. pending signal.
+ * Otherwise, function returns one-past-the-last PFN of isolated page
+ * (which may be greater than end_pfn if end fell in a middle of a THP page).
+ */
+unsigned long
+isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
+ unsigned long end_pfn)
+{
+ unsigned long pfn, block_end_pfn;
+
+ /* Scan block by block. First and last block may be incomplete */
+ pfn = start_pfn;
+ block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
+
+ for (; pfn < end_pfn; pfn = block_end_pfn,
+ block_end_pfn += pageblock_nr_pages) {
+
+ block_end_pfn = min(block_end_pfn, end_pfn);
+
+ if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
+ continue;
+
+ pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
+ ISOLATE_UNEVICTABLE);
+
+ /*
+ * In case of fatal failure, release everything that might
+ * have been isolated in the previous iteration, and signal
+ * the failure back to caller.
+ */
+ if (!pfn) {
+ putback_movable_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ break;
+ }
+
+ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
+ break;
+ }
+ acct_isolated(cc->zone, cc);
+
+ return pfn;
+}
+
+#endif /* CONFIG_COMPACTION || CONFIG_CMA */
+#ifdef CONFIG_COMPACTION
+
+/* Returns true if the page is within a block suitable for migration to */
+static bool suitable_migration_target(struct page *page)
+{
+ /* If the page is a large free page, then disallow migration */
+ if (PageBuddy(page)) {
+ /*
+ * We are checking page_order without zone->lock taken. But
+ * the only small danger is that we skip a potentially suitable
+ * pageblock, so it's not worth to check order for valid range.
+ */
+ if (page_order_unsafe(page) >= pageblock_order)
+ return false;
+ }
+
+ /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
+ if (migrate_async_suitable(get_pageblock_migratetype(page)))
+ return true;
+
+ /* Otherwise skip the block */
+ return false;
+}
+
+/*
+ * Based on information in the current compact_control, find blocks
+ * suitable for isolating free pages from and then isolate them.
+ */
+static void isolate_freepages(struct compact_control *cc)
+{
+ struct zone *zone = cc->zone;
+ struct page *page;
+ unsigned long block_start_pfn; /* start of current pageblock */
+ unsigned long isolate_start_pfn; /* exact pfn we start at */
+ unsigned long block_end_pfn; /* end of current pageblock */
+ unsigned long low_pfn; /* lowest pfn scanner is able to scan */
+ struct list_head *freelist = &cc->freepages;
+
+ /*
+ * Initialise the free scanner. The starting point is where we last
+ * successfully isolated from, zone-cached value, or the end of the
+ * zone when isolating for the first time. For looping we also need
+ * this pfn aligned down to the pageblock boundary, because we do
+ * block_start_pfn -= pageblock_nr_pages in the for loop.
+ * For ending point, take care when isolating in last pageblock of a
+ * a zone which ends in the middle of a pageblock.
+ * The low boundary is the end of the pageblock the migration scanner
+ * is using.
+ */
+ isolate_start_pfn = cc->free_pfn;
+ block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1);
+ block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
+ zone_end_pfn(zone));
+ low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages);
+
+ /*
+ * Isolate free pages until enough are available to migrate the
+ * pages on cc->migratepages. We stop searching if the migrate
+ * and free page scanners meet or enough free pages are isolated.
+ */
+ for (; block_start_pfn >= low_pfn &&
+ cc->nr_migratepages > cc->nr_freepages;
+ block_end_pfn = block_start_pfn,
+ block_start_pfn -= pageblock_nr_pages,
+ isolate_start_pfn = block_start_pfn) {
+
+ /*
+ * This can iterate a massively long zone without finding any
+ * suitable migration targets, so periodically check if we need
+ * to schedule, or even abort async compaction.
+ */
+ if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
+ && compact_should_abort(cc))
+ break;
+
+ page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
+ zone);
+ if (!page)
+ continue;
+
+ /* Check the block is suitable for migration */
+ if (!suitable_migration_target(page))
+ continue;
+
+ /* If isolation recently failed, do not retry */
+ if (!isolation_suitable(cc, page))
+ continue;
+
+ /* Found a block suitable for isolating free pages from. */
+ isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, freelist, false);
+
+ /*
+ * Remember where the free scanner should restart next time,
+ * which is where isolate_freepages_block() left off.
+ * But if it scanned the whole pageblock, isolate_start_pfn
+ * now points at block_end_pfn, which is the start of the next
+ * pageblock.
+ * In that case we will however want to restart at the start
+ * of the previous pageblock.
+ */
+ cc->free_pfn = (isolate_start_pfn < block_end_pfn) ?
+ isolate_start_pfn :
+ block_start_pfn - pageblock_nr_pages;
+
+ /*
+ * isolate_freepages_block() might have aborted due to async
+ * compaction being contended
+ */
+ if (cc->contended)
+ break;
+ }
+
+ /* split_free_page does not map the pages */
+ map_pages(freelist);
+
+ /*
+ * If we crossed the migrate scanner, we want to keep it that way
+ * so that compact_finished() may detect this
+ */
+ if (block_start_pfn < low_pfn)
+ cc->free_pfn = cc->migrate_pfn;
+}
+
+/*
+ * This is a migrate-callback that "allocates" freepages by taking pages
+ * from the isolated freelists in the block we are migrating to.
+ */
+static struct page *compaction_alloc(struct page *migratepage,
+ unsigned long data,
+ int **result)
+{
+ struct compact_control *cc = (struct compact_control *)data;
+ struct page *freepage;
+
+ /*
+ * Isolate free pages if necessary, and if we are not aborting due to
+ * contention.
+ */
+ if (list_empty(&cc->freepages)) {
+ if (!cc->contended)
+ isolate_freepages(cc);
+
+ if (list_empty(&cc->freepages))
+ return NULL;
+ }
+
+ freepage = list_entry(cc->freepages.next, struct page, lru);
+ list_del(&freepage->lru);
+ cc->nr_freepages--;
+
+ return freepage;
+}
+
+/*
+ * This is a migrate-callback that "frees" freepages back to the isolated
+ * freelist. All pages on the freelist are from the same zone, so there is no
+ * special handling needed for NUMA.
+ */
+static void compaction_free(struct page *page, unsigned long data)
+{
+ struct compact_control *cc = (struct compact_control *)data;
+
+ list_add(&page->lru, &cc->freepages);
+ cc->nr_freepages++;
+}
+
+/* possible outcome of isolate_migratepages */
+typedef enum {
+ ISOLATE_ABORT, /* Abort compaction now */
+ ISOLATE_NONE, /* No pages isolated, continue scanning */
+ ISOLATE_SUCCESS, /* Pages isolated, migrate */
+} isolate_migrate_t;
+
+/*
+ * Allow userspace to control policy on scanning the unevictable LRU for
+ * compactable pages.
+ */
+int sysctl_compact_unevictable_allowed __read_mostly = 1;
+
+/*
+ * Isolate all pages that can be migrated from the first suitable block,
+ * starting at the block pointed to by the migrate scanner pfn within
+ * compact_control.
+ */
+static isolate_migrate_t isolate_migratepages(struct zone *zone,
+ struct compact_control *cc)
+{
+ unsigned long low_pfn, end_pfn;
+ struct page *page;
+ const isolate_mode_t isolate_mode =
+ (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
+ (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);
+
+ /*
+ * Start at where we last stopped, or beginning of the zone as
+ * initialized by compact_zone()
+ */
+ low_pfn = cc->migrate_pfn;
+
+ /* Only scan within a pageblock boundary */
+ end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
+
+ /*
+ * Iterate over whole pageblocks until we find the first suitable.
+ * Do not cross the free scanner.
+ */
+ for (; end_pfn <= cc->free_pfn;
+ low_pfn = end_pfn, end_pfn += pageblock_nr_pages) {
+
+ /*
+ * This can potentially iterate a massively long zone with
+ * many pageblocks unsuitable, so periodically check if we
+ * need to schedule, or even abort async compaction.
+ */
+ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages))
+ && compact_should_abort(cc))
+ break;
+
+ page = pageblock_pfn_to_page(low_pfn, end_pfn, zone);
+ if (!page)
+ continue;
+
+ /* If isolation recently failed, do not retry */
+ if (!isolation_suitable(cc, page))
+ continue;
+
+ /*
+ * For async compaction, also only scan in MOVABLE blocks.
+ * Async compaction is optimistic to see if the minimum amount
+ * of work satisfies the allocation.
+ */
+ if (cc->mode == MIGRATE_ASYNC &&
+ !migrate_async_suitable(get_pageblock_migratetype(page)))
+ continue;
+
+ /* Perform the isolation */
+ low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
+ isolate_mode);
+
+ if (!low_pfn || cc->contended) {
+ acct_isolated(zone, cc);
+ return ISOLATE_ABORT;
+ }
+
+ /*
+ * Either we isolated something and proceed with migration. Or
+ * we failed and compact_zone should decide if we should
+ * continue or not.
+ */
+ break;
+ }
+
+ acct_isolated(zone, cc);
+ /*
+ * Record where migration scanner will be restarted. If we end up in
+ * the same pageblock as the free scanner, make the scanners fully
+ * meet so that compact_finished() terminates compaction.
+ */
+ cc->migrate_pfn = (end_pfn <= cc->free_pfn) ? low_pfn : cc->free_pfn;
+
+ return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
+}
+
+static int __compact_finished(struct zone *zone, struct compact_control *cc,
+ const int migratetype)
+{
+ unsigned int order;
+ unsigned long watermark;
+
+ if (cc->contended || fatal_signal_pending(current))
+ return COMPACT_PARTIAL;
+
+ /* Compaction run completes if the migrate and free scanner meet */
+ if (cc->free_pfn <= cc->migrate_pfn) {
+ /* Let the next compaction start anew. */
+ zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
+ zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
+ zone->compact_cached_free_pfn = zone_end_pfn(zone);
+
+ /*
+ * Mark that the PG_migrate_skip information should be cleared
+ * by kswapd when it goes to sleep. kswapd does not set the
+ * flag itself as the decision to be clear should be directly
+ * based on an allocation request.
+ */
+ if (!current_is_kswapd())
+ zone->compact_blockskip_flush = true;
+
+ return COMPACT_COMPLETE;
+ }
+
+ /*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+ if (cc->order == -1)
+ return COMPACT_CONTINUE;
+
+ /* Compaction run is not finished if the watermark is not met */
+ watermark = low_wmark_pages(zone);
+
+ if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
+ cc->alloc_flags))
+ return COMPACT_CONTINUE;
+
+ /* Direct compactor: Is a suitable page free? */
+ for (order = cc->order; order < MAX_ORDER; order++) {
+ struct free_area *area = &zone->free_area[order];
+ bool can_steal;
+
+ /* Job done if page is free of the right migratetype */
+ if (!list_empty(&area->free_list[migratetype]))
+ return COMPACT_PARTIAL;
+
+#ifdef CONFIG_CMA
+ /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
+ if (migratetype == MIGRATE_MOVABLE &&
+ !list_empty(&area->free_list[MIGRATE_CMA]))
+ return COMPACT_PARTIAL;
+#endif
+ /*
+ * Job done if allocation would steal freepages from
+ * other migratetype buddy lists.
+ */
+ if (find_suitable_fallback(area, order, migratetype,
+ true, &can_steal) != -1)
+ return COMPACT_PARTIAL;
+ }
+
+ return COMPACT_NO_SUITABLE_PAGE;
+}
+
+static int compact_finished(struct zone *zone, struct compact_control *cc,
+ const int migratetype)
+{
+ int ret;
+
+ ret = __compact_finished(zone, cc, migratetype);
+ trace_mm_compaction_finished(zone, cc->order, ret);
+ if (ret == COMPACT_NO_SUITABLE_PAGE)
+ ret = COMPACT_CONTINUE;
+
+ return ret;
+}
+
+/*
+ * compaction_suitable: Is this suitable to run compaction on this zone now?
+ * Returns
+ * COMPACT_SKIPPED - If there are too few free pages for compaction
+ * COMPACT_PARTIAL - If the allocation would succeed without compaction
+ * COMPACT_CONTINUE - If compaction should run now
+ */
+static unsigned long __compaction_suitable(struct zone *zone, int order,
+ int alloc_flags, int classzone_idx)
+{
+ int fragindex;
+ unsigned long watermark;
+
+ /*
+ * order == -1 is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+ if (order == -1)
+ return COMPACT_CONTINUE;
+
+ watermark = low_wmark_pages(zone);
+ /*
+ * If watermarks for high-order allocation are already met, there
+ * should be no need for compaction at all.
+ */
+ if (zone_watermark_ok(zone, order, watermark, classzone_idx,
+ alloc_flags))
+ return COMPACT_PARTIAL;
+
+ /*
+ * Watermarks for order-0 must be met for compaction. Note the 2UL.
+ * This is because during migration, copies of pages need to be
+ * allocated and for a short time, the footprint is higher
+ */
+ watermark += (2UL << order);
+ if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags))
+ return COMPACT_SKIPPED;
+
+ /*
+ * fragmentation index determines if allocation failures are due to
+ * low memory or external fragmentation
+ *
+ * index of -1000 would imply allocations might succeed depending on
+ * watermarks, but we already failed the high-order watermark check
+ * index towards 0 implies failure is due to lack of memory
+ * index towards 1000 implies failure is due to fragmentation
+ *
+ * Only compact if a failure would be due to fragmentation.
+ */
+ fragindex = fragmentation_index(zone, order);
+ if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
+ return COMPACT_NOT_SUITABLE_ZONE;
+
+ return COMPACT_CONTINUE;
+}
+
+unsigned long compaction_suitable(struct zone *zone, int order,
+ int alloc_flags, int classzone_idx)
+{
+ unsigned long ret;
+
+ ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx);
+ trace_mm_compaction_suitable(zone, order, ret);
+ if (ret == COMPACT_NOT_SUITABLE_ZONE)
+ ret = COMPACT_SKIPPED;
+
+ return ret;
+}
+
+static int compact_zone(struct zone *zone, struct compact_control *cc)
+{
+ int ret;
+ unsigned long start_pfn = zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(zone);
+ const int migratetype = gfpflags_to_migratetype(cc->gfp_mask);
+ const bool sync = cc->mode != MIGRATE_ASYNC;
+ unsigned long last_migrated_pfn = 0;
+
+ ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
+ cc->classzone_idx);
+ switch (ret) {
+ case COMPACT_PARTIAL:
+ case COMPACT_SKIPPED:
+ /* Compaction is likely to fail */
+ return ret;
+ case COMPACT_CONTINUE:
+ /* Fall through to compaction */
+ ;
+ }
+
+ /*
+ * Clear pageblock skip if there were failures recently and compaction
+ * is about to be retried after being deferred. kswapd does not do
+ * this reset as it'll reset the cached information when going to sleep.
+ */
+ if (compaction_restarting(zone, cc->order) && !current_is_kswapd())
+ __reset_isolation_suitable(zone);
+
+ /*
+ * Setup to move all movable pages to the end of the zone. Used cached
+ * information on where the scanners should start but check that it
+ * is initialised by ensuring the values are within zone boundaries.
+ */
+ cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
+ cc->free_pfn = zone->compact_cached_free_pfn;
+ if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
+ cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
+ zone->compact_cached_free_pfn = cc->free_pfn;
+ }
+ if (cc->migrate_pfn < start_pfn || cc->migrate_pfn > end_pfn) {
+ cc->migrate_pfn = start_pfn;
+ zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
+ zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
+ }
+
+ trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
+ cc->free_pfn, end_pfn, sync);
+
+ migrate_prep_local();
+
+ while ((ret = compact_finished(zone, cc, migratetype)) ==
+ COMPACT_CONTINUE) {
+ int err;
+ unsigned long isolate_start_pfn = cc->migrate_pfn;
+
+ switch (isolate_migratepages(zone, cc)) {
+ case ISOLATE_ABORT:
+ ret = COMPACT_PARTIAL;
+ putback_movable_pages(&cc->migratepages);
+ cc->nr_migratepages = 0;
+ goto out;
+ case ISOLATE_NONE:
+ /*
+ * We haven't isolated and migrated anything, but
+ * there might still be unflushed migrations from
+ * previous cc->order aligned block.
+ */
+ goto check_drain;
+ case ISOLATE_SUCCESS:
+ ;
+ }
+
+ err = migrate_pages(&cc->migratepages, compaction_alloc,
+ compaction_free, (unsigned long)cc, cc->mode,
+ MR_COMPACTION);
+
+ trace_mm_compaction_migratepages(cc->nr_migratepages, err,
+ &cc->migratepages);
+
+ /* All pages were either migrated or will be released */
+ cc->nr_migratepages = 0;
+ if (err) {
+ putback_movable_pages(&cc->migratepages);
+ /*
+ * migrate_pages() may return -ENOMEM when scanners meet
+ * and we want compact_finished() to detect it
+ */
+ if (err == -ENOMEM && cc->free_pfn > cc->migrate_pfn) {
+ ret = COMPACT_PARTIAL;
+ goto out;
+ }
+ }
+
+ /*
+ * Record where we could have freed pages by migration and not
+ * yet flushed them to buddy allocator. We use the pfn that
+ * isolate_migratepages() started from in this loop iteration
+ * - this is the lowest page that could have been isolated and
+ * then freed by migration.
+ */
+ if (!last_migrated_pfn)
+ last_migrated_pfn = isolate_start_pfn;
+
+check_drain:
+ /*
+ * Has the migration scanner moved away from the previous
+ * cc->order aligned block where we migrated from? If yes,
+ * flush the pages that were freed, so that they can merge and
+ * compact_finished() can detect immediately if allocation
+ * would succeed.
+ */
+ if (cc->order > 0 && last_migrated_pfn) {
+ int cpu;
+ unsigned long current_block_start =
+ cc->migrate_pfn & ~((1UL << cc->order) - 1);
+
+ if (last_migrated_pfn < current_block_start) {
+ cpu = get_cpu_light();
+ local_lock_irq(swapvec_lock);
+ lru_add_drain_cpu(cpu);
+ local_unlock_irq(swapvec_lock);
+ drain_local_pages(zone);
+ put_cpu_light();
+ /* No more flushing until we migrate again */
+ last_migrated_pfn = 0;
+ }
+ }
+
+ }
+
+out:
+ /*
+ * Release free pages and update where the free scanner should restart,
+ * so we don't leave any returned pages behind in the next attempt.
+ */
+ if (cc->nr_freepages > 0) {
+ unsigned long free_pfn = release_freepages(&cc->freepages);
+
+ cc->nr_freepages = 0;
+ VM_BUG_ON(free_pfn == 0);
+ /* The cached pfn is always the first in a pageblock */
+ free_pfn &= ~(pageblock_nr_pages-1);
+ /*
+ * Only go back, not forward. The cached pfn might have been
+ * already reset to zone end in compact_finished()
+ */
+ if (free_pfn > zone->compact_cached_free_pfn)
+ zone->compact_cached_free_pfn = free_pfn;
+ }
+
+ trace_mm_compaction_end(start_pfn, cc->migrate_pfn,
+ cc->free_pfn, end_pfn, sync, ret);
+
+ return ret;
+}
+
+static unsigned long compact_zone_order(struct zone *zone, int order,
+ gfp_t gfp_mask, enum migrate_mode mode, int *contended,
+ int alloc_flags, int classzone_idx)
+{
+ unsigned long ret;
+ struct compact_control cc = {
+ .nr_freepages = 0,
+ .nr_migratepages = 0,
+ .order = order,
+ .gfp_mask = gfp_mask,
+ .zone = zone,
+ .mode = mode,
+ .alloc_flags = alloc_flags,
+ .classzone_idx = classzone_idx,
+ };
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ ret = compact_zone(zone, &cc);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+
+ *contended = cc.contended;
+ return ret;
+}
+
+int sysctl_extfrag_threshold = 500;
+
+/**
+ * try_to_compact_pages - Direct compact to satisfy a high-order allocation
+ * @gfp_mask: The GFP mask of the current allocation
+ * @order: The order of the current allocation
+ * @alloc_flags: The allocation flags of the current allocation
+ * @ac: The context of current allocation
+ * @mode: The migration mode for async, sync light, or sync migration
+ * @contended: Return value that determines if compaction was aborted due to
+ * need_resched() or lock contention
+ *
+ * This is the main entry point for direct page compaction.
+ */
+unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
+ int alloc_flags, const struct alloc_context *ac,
+ enum migrate_mode mode, int *contended)
+{
+ int may_enter_fs = gfp_mask & __GFP_FS;
+ int may_perform_io = gfp_mask & __GFP_IO;
+ struct zoneref *z;
+ struct zone *zone;
+ int rc = COMPACT_DEFERRED;
+ int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */
+
+ *contended = COMPACT_CONTENDED_NONE;
+
+ /* Check if the GFP flags allow compaction */
+ if (!order || !may_enter_fs || !may_perform_io)
+ return COMPACT_SKIPPED;
+
+ trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
+
+ /* Compact each zone in the list */
+ for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
+ ac->nodemask) {
+ int status;
+ int zone_contended;
+
+ if (compaction_deferred(zone, order))
+ continue;
+
+ status = compact_zone_order(zone, order, gfp_mask, mode,
+ &zone_contended, alloc_flags,
+ ac->classzone_idx);
+ rc = max(status, rc);
+ /*
+ * It takes at least one zone that wasn't lock contended
+ * to clear all_zones_contended.
+ */
+ all_zones_contended &= zone_contended;
+
+ /* If a normal allocation would succeed, stop compacting */
+ if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
+ ac->classzone_idx, alloc_flags)) {
+ /*
+ * We think the allocation will succeed in this zone,
+ * but it is not certain, hence the false. The caller
+ * will repeat this with true if allocation indeed
+ * succeeds in this zone.
+ */
+ compaction_defer_reset(zone, order, false);
+ /*
+ * It is possible that async compaction aborted due to
+ * need_resched() and the watermarks were ok thanks to
+ * somebody else freeing memory. The allocation can
+ * however still fail so we better signal the
+ * need_resched() contention anyway (this will not
+ * prevent the allocation attempt).
+ */
+ if (zone_contended == COMPACT_CONTENDED_SCHED)
+ *contended = COMPACT_CONTENDED_SCHED;
+
+ goto break_loop;
+ }
+
+ if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) {
+ /*
+ * We think that allocation won't succeed in this zone
+ * so we defer compaction there. If it ends up
+ * succeeding after all, it will be reset.
+ */
+ defer_compaction(zone, order);
+ }
+
+ /*
+ * We might have stopped compacting due to need_resched() in
+ * async compaction, or due to a fatal signal detected. In that
+ * case do not try further zones and signal need_resched()
+ * contention.
+ */
+ if ((zone_contended == COMPACT_CONTENDED_SCHED)
+ || fatal_signal_pending(current)) {
+ *contended = COMPACT_CONTENDED_SCHED;
+ goto break_loop;
+ }
+
+ continue;
+break_loop:
+ /*
+ * We might not have tried all the zones, so be conservative
+ * and assume they are not all lock contended.
+ */
+ all_zones_contended = 0;
+ break;
+ }
+
+ /*
+ * If at least one zone wasn't deferred or skipped, we report if all
+ * zones that were tried were lock contended.
+ */
+ if (rc > COMPACT_SKIPPED && all_zones_contended)
+ *contended = COMPACT_CONTENDED_LOCK;
+
+ return rc;
+}
+
+
+/* Compact all zones within a node */
+static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
+{
+ int zoneid;
+ struct zone *zone;
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+
+ zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ cc->nr_freepages = 0;
+ cc->nr_migratepages = 0;
+ cc->zone = zone;
+ INIT_LIST_HEAD(&cc->freepages);
+ INIT_LIST_HEAD(&cc->migratepages);
+
+ /*
+ * When called via /proc/sys/vm/compact_memory
+ * this makes sure we compact the whole zone regardless of
+ * cached scanner positions.
+ */
+ if (cc->order == -1)
+ __reset_isolation_suitable(zone);
+
+ if (cc->order == -1 || !compaction_deferred(zone, cc->order))
+ compact_zone(zone, cc);
+
+ if (cc->order > 0) {
+ if (zone_watermark_ok(zone, cc->order,
+ low_wmark_pages(zone), 0, 0))
+ compaction_defer_reset(zone, cc->order, false);
+ }
+
+ VM_BUG_ON(!list_empty(&cc->freepages));
+ VM_BUG_ON(!list_empty(&cc->migratepages));
+ }
+}
+
+void compact_pgdat(pg_data_t *pgdat, int order)
+{
+ struct compact_control cc = {
+ .order = order,
+ .mode = MIGRATE_ASYNC,
+ };
+
+ if (!order)
+ return;
+
+ __compact_pgdat(pgdat, &cc);
+}
+
+static void compact_node(int nid)
+{
+ struct compact_control cc = {
+ .order = -1,
+ .mode = MIGRATE_SYNC,
+ .ignore_skip_hint = true,
+ };
+
+ __compact_pgdat(NODE_DATA(nid), &cc);
+}
+
+/* Compact all nodes in the system */
+static void compact_nodes(void)
+{
+ int nid;
+
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ for_each_online_node(nid)
+ compact_node(nid);
+}
+
+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
+
+/* This is the entry point for compacting all nodes via /proc/sys/vm */
+int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ compact_nodes();
+
+ return 0;
+}
+
+int sysctl_extfrag_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ proc_dointvec_minmax(table, write, buffer, length, ppos);
+
+ return 0;
+}
+
+#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+static ssize_t sysfs_compact_node(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int nid = dev->id;
+
+ if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ compact_node(nid);
+ }
+
+ return count;
+}
+static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
+
+int compaction_register_node(struct node *node)
+{
+ return device_create_file(&node->dev, &dev_attr_compact);
+}
+
+void compaction_unregister_node(struct node *node)
+{
+ return device_remove_file(&node->dev, &dev_attr_compact);
+}
+#endif /* CONFIG_SYSFS && CONFIG_NUMA */
+
+#endif /* CONFIG_COMPACTION */
Code Review / kvmfornfv.git / blobdiff