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![David Rientjes](/assets/img/avatar_default.png)
We've been getting warnings about an excessive amount of time spent allocating pages for migration during memory compaction without scheduling. isolate_freepages_block() already periodically checks for contended locks or the need to schedule, but isolate_freepages() never does. When a zone is massively long and no suitable targets can be found, this iteration can be quite expensive without ever doing cond_resched(). Check periodically for the need to reschedule while the compaction free scanner iterates. Signed-off-by: David Rientjes <rientjes@google.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1219 lines
32 KiB
C
1219 lines
32 KiB
C
/*
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* linux/mm/compaction.c
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*
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* Memory compaction for the reduction of external fragmentation. Note that
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* this heavily depends upon page migration to do all the real heavy
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* lifting
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*
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* Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
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*/
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#include <linux/swap.h>
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#include <linux/migrate.h>
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#include <linux/compaction.h>
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#include <linux/mm_inline.h>
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#include <linux/backing-dev.h>
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#include <linux/sysctl.h>
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#include <linux/sysfs.h>
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#include <linux/balloon_compaction.h>
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#include <linux/page-isolation.h>
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#include "internal.h"
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#ifdef CONFIG_COMPACTION
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static inline void count_compact_event(enum vm_event_item item)
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{
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count_vm_event(item);
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}
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static inline void count_compact_events(enum vm_event_item item, long delta)
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{
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count_vm_events(item, delta);
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}
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#else
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#define count_compact_event(item) do { } while (0)
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#define count_compact_events(item, delta) do { } while (0)
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#endif
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#if defined CONFIG_COMPACTION || defined CONFIG_CMA
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#define CREATE_TRACE_POINTS
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#include <trace/events/compaction.h>
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static unsigned long release_freepages(struct list_head *freelist)
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{
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struct page *page, *next;
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unsigned long count = 0;
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list_for_each_entry_safe(page, next, freelist, lru) {
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list_del(&page->lru);
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__free_page(page);
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count++;
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}
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return count;
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}
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static void map_pages(struct list_head *list)
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{
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struct page *page;
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list_for_each_entry(page, list, lru) {
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arch_alloc_page(page, 0);
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kernel_map_pages(page, 1, 1);
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}
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}
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static inline bool migrate_async_suitable(int migratetype)
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{
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return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
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}
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#ifdef CONFIG_COMPACTION
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/* Returns true if the pageblock should be scanned for pages to isolate. */
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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if (cc->ignore_skip_hint)
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return true;
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return !get_pageblock_skip(page);
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}
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/*
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* This function is called to clear all cached information on pageblocks that
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* should be skipped for page isolation when the migrate and free page scanner
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* meet.
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*/
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static void __reset_isolation_suitable(struct zone *zone)
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{
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unsigned long start_pfn = zone->zone_start_pfn;
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unsigned long end_pfn = zone_end_pfn(zone);
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unsigned long pfn;
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zone->compact_cached_migrate_pfn = start_pfn;
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zone->compact_cached_free_pfn = end_pfn;
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zone->compact_blockskip_flush = false;
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/* Walk the zone and mark every pageblock as suitable for isolation */
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for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
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struct page *page;
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cond_resched();
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if (!pfn_valid(pfn))
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continue;
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page = pfn_to_page(pfn);
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if (zone != page_zone(page))
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continue;
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clear_pageblock_skip(page);
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}
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}
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void reset_isolation_suitable(pg_data_t *pgdat)
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{
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int zoneid;
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for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
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struct zone *zone = &pgdat->node_zones[zoneid];
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if (!populated_zone(zone))
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continue;
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/* Only flush if a full compaction finished recently */
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if (zone->compact_blockskip_flush)
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__reset_isolation_suitable(zone);
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}
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}
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/*
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* If no pages were isolated then mark this pageblock to be skipped in the
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* future. The information is later cleared by __reset_isolation_suitable().
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*/
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static void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long nr_isolated,
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bool migrate_scanner)
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{
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struct zone *zone = cc->zone;
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if (!page)
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return;
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if (!nr_isolated) {
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unsigned long pfn = page_to_pfn(page);
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set_pageblock_skip(page);
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/* Update where compaction should restart */
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if (migrate_scanner) {
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if (!cc->finished_update_migrate &&
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pfn > zone->compact_cached_migrate_pfn)
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zone->compact_cached_migrate_pfn = pfn;
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} else {
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if (!cc->finished_update_free &&
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pfn < zone->compact_cached_free_pfn)
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zone->compact_cached_free_pfn = pfn;
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}
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}
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}
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#else
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static inline bool isolation_suitable(struct compact_control *cc,
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struct page *page)
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{
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return true;
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}
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static void update_pageblock_skip(struct compact_control *cc,
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struct page *page, unsigned long nr_isolated,
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bool migrate_scanner)
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{
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}
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#endif /* CONFIG_COMPACTION */
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static inline bool should_release_lock(spinlock_t *lock)
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{
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return need_resched() || spin_is_contended(lock);
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}
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/*
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* Compaction requires the taking of some coarse locks that are potentially
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* very heavily contended. Check if the process needs to be scheduled or
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* if the lock is contended. For async compaction, back out in the event
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* if contention is severe. For sync compaction, schedule.
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*
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* Returns true if the lock is held.
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* Returns false if the lock is released and compaction should abort
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*/
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static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
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bool locked, struct compact_control *cc)
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{
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if (should_release_lock(lock)) {
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if (locked) {
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spin_unlock_irqrestore(lock, *flags);
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locked = false;
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}
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/* async aborts if taking too long or contended */
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if (!cc->sync) {
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cc->contended = true;
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return false;
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}
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cond_resched();
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}
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if (!locked)
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spin_lock_irqsave(lock, *flags);
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return true;
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}
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static inline bool compact_trylock_irqsave(spinlock_t *lock,
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unsigned long *flags, struct compact_control *cc)
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{
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return compact_checklock_irqsave(lock, flags, false, cc);
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}
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/* Returns true if the page is within a block suitable for migration to */
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static bool suitable_migration_target(struct page *page)
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{
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int migratetype = get_pageblock_migratetype(page);
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/* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
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if (migratetype == MIGRATE_RESERVE)
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return false;
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if (is_migrate_isolate(migratetype))
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return false;
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/* If the page is a large free page, then allow migration */
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if (PageBuddy(page) && page_order(page) >= pageblock_order)
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return true;
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/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
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if (migrate_async_suitable(migratetype))
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return true;
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/* Otherwise skip the block */
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return false;
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}
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/*
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* Isolate free pages onto a private freelist. Caller must hold zone->lock.
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* If @strict is true, will abort returning 0 on any invalid PFNs or non-free
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* pages inside of the pageblock (even though it may still end up isolating
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* some pages).
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*/
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static unsigned long isolate_freepages_block(struct compact_control *cc,
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unsigned long blockpfn,
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unsigned long end_pfn,
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struct list_head *freelist,
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bool strict)
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{
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int nr_scanned = 0, total_isolated = 0;
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struct page *cursor, *valid_page = NULL;
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unsigned long nr_strict_required = end_pfn - blockpfn;
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unsigned long flags;
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bool locked = false;
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cursor = pfn_to_page(blockpfn);
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/* Isolate free pages. */
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for (; blockpfn < end_pfn; blockpfn++, cursor++) {
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int isolated, i;
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struct page *page = cursor;
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nr_scanned++;
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if (!pfn_valid_within(blockpfn))
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continue;
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if (!valid_page)
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valid_page = page;
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if (!PageBuddy(page))
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continue;
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/*
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* The zone lock must be held to isolate freepages.
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* Unfortunately this is a very coarse lock and can be
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* heavily contended if there are parallel allocations
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* or parallel compactions. For async compaction do not
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* spin on the lock and we acquire the lock as late as
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* possible.
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*/
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locked = compact_checklock_irqsave(&cc->zone->lock, &flags,
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locked, cc);
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if (!locked)
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break;
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/* Recheck this is a suitable migration target under lock */
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if (!strict && !suitable_migration_target(page))
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break;
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/* Recheck this is a buddy page under lock */
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if (!PageBuddy(page))
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continue;
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/* Found a free page, break it into order-0 pages */
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isolated = split_free_page(page);
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if (!isolated && strict)
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break;
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total_isolated += isolated;
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for (i = 0; i < isolated; i++) {
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list_add(&page->lru, freelist);
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page++;
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}
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/* If a page was split, advance to the end of it */
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if (isolated) {
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blockpfn += isolated - 1;
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cursor += isolated - 1;
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}
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}
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trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
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/*
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* If strict isolation is requested by CMA then check that all the
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* pages requested were isolated. If there were any failures, 0 is
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* returned and CMA will fail.
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*/
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if (strict && nr_strict_required > total_isolated)
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total_isolated = 0;
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if (locked)
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spin_unlock_irqrestore(&cc->zone->lock, flags);
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/* Update the pageblock-skip if the whole pageblock was scanned */
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if (blockpfn == end_pfn)
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update_pageblock_skip(cc, valid_page, total_isolated, false);
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count_compact_events(COMPACTFREE_SCANNED, nr_scanned);
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if (total_isolated)
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count_compact_events(COMPACTISOLATED, total_isolated);
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return total_isolated;
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}
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/**
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* isolate_freepages_range() - isolate free pages.
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* @start_pfn: The first PFN to start isolating.
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* @end_pfn: The one-past-last PFN.
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*
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* Non-free pages, invalid PFNs, or zone boundaries within the
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* [start_pfn, end_pfn) range are considered errors, cause function to
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* undo its actions and return zero.
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*
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* Otherwise, function returns one-past-the-last PFN of isolated page
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* (which may be greater then end_pfn if end fell in a middle of
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* a free page).
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*/
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unsigned long
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isolate_freepages_range(struct compact_control *cc,
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unsigned long start_pfn, unsigned long end_pfn)
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{
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unsigned long isolated, pfn, block_end_pfn;
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LIST_HEAD(freelist);
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for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) {
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if (!pfn_valid(pfn) || cc->zone != page_zone(pfn_to_page(pfn)))
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break;
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/*
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* On subsequent iterations ALIGN() is actually not needed,
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* but we keep it that we not to complicate the code.
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*/
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block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
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block_end_pfn = min(block_end_pfn, end_pfn);
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isolated = isolate_freepages_block(cc, pfn, block_end_pfn,
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&freelist, true);
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/*
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* In strict mode, isolate_freepages_block() returns 0 if
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* there are any holes in the block (ie. invalid PFNs or
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* non-free pages).
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*/
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if (!isolated)
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break;
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/*
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* If we managed to isolate pages, it is always (1 << n) *
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* pageblock_nr_pages for some non-negative n. (Max order
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* page may span two pageblocks).
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*/
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}
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/* split_free_page does not map the pages */
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map_pages(&freelist);
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if (pfn < end_pfn) {
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/* Loop terminated early, cleanup. */
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release_freepages(&freelist);
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return 0;
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}
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/* We don't use freelists for anything. */
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return pfn;
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}
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/* Update the number of anon and file isolated pages in the zone */
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static void acct_isolated(struct zone *zone, bool locked, struct compact_control *cc)
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{
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struct page *page;
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unsigned int count[2] = { 0, };
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list_for_each_entry(page, &cc->migratepages, lru)
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count[!!page_is_file_cache(page)]++;
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/* If locked we can use the interrupt unsafe versions */
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if (locked) {
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__mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
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__mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
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} else {
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mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
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mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
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}
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}
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/* Similar to reclaim, but different enough that they don't share logic */
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static bool too_many_isolated(struct zone *zone)
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{
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unsigned long active, inactive, isolated;
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inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
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zone_page_state(zone, NR_INACTIVE_ANON);
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active = zone_page_state(zone, NR_ACTIVE_FILE) +
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zone_page_state(zone, NR_ACTIVE_ANON);
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isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
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zone_page_state(zone, NR_ISOLATED_ANON);
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return isolated > (inactive + active) / 2;
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}
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/**
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* isolate_migratepages_range() - isolate all migrate-able pages in range.
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* @zone: Zone pages are in.
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* @cc: Compaction control structure.
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* @low_pfn: The first PFN of the range.
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* @end_pfn: The one-past-the-last PFN of the range.
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* @unevictable: true if it allows to isolate unevictable pages
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*
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* Isolate all pages that can be migrated from the range specified by
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* [low_pfn, end_pfn). Returns zero if there is a fatal signal
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* pending), otherwise PFN of the first page that was not scanned
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* (which may be both less, equal to or more then end_pfn).
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*
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* Assumes that cc->migratepages is empty and cc->nr_migratepages is
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* zero.
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*
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* Apart from cc->migratepages and cc->nr_migratetypes this function
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* does not modify any cc's fields, in particular it does not modify
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* (or read for that matter) cc->migrate_pfn.
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*/
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unsigned long
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isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
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unsigned long low_pfn, unsigned long end_pfn, bool unevictable)
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{
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unsigned long last_pageblock_nr = 0, pageblock_nr;
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unsigned long nr_scanned = 0, nr_isolated = 0;
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struct list_head *migratelist = &cc->migratepages;
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isolate_mode_t mode = 0;
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struct lruvec *lruvec;
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unsigned long flags;
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bool locked = false;
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struct page *page = NULL, *valid_page = NULL;
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/*
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* Ensure that there are not too many pages isolated from the LRU
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* list by either parallel reclaimers or compaction. If there are,
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* delay for some time until fewer pages are isolated
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*/
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while (unlikely(too_many_isolated(zone))) {
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/* async migration should just abort */
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if (!cc->sync)
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return 0;
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congestion_wait(BLK_RW_ASYNC, HZ/10);
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|
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if (fatal_signal_pending(current))
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return 0;
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}
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|
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/* Time to isolate some pages for migration */
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cond_resched();
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for (; low_pfn < end_pfn; low_pfn++) {
|
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/* give a chance to irqs before checking need_resched() */
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if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
|
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if (should_release_lock(&zone->lru_lock)) {
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spin_unlock_irqrestore(&zone->lru_lock, flags);
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locked = false;
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}
|
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}
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/*
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* migrate_pfn does not necessarily start aligned to a
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* pageblock. Ensure that pfn_valid is called when moving
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* into a new MAX_ORDER_NR_PAGES range in case of large
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* memory holes within the zone
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*/
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if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) {
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if (!pfn_valid(low_pfn)) {
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low_pfn += MAX_ORDER_NR_PAGES - 1;
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continue;
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}
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}
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|
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if (!pfn_valid_within(low_pfn))
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continue;
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nr_scanned++;
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|
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/*
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* Get the page and ensure the page is within the same zone.
|
|
* See the comment in isolate_freepages about overlapping
|
|
* nodes. It is deliberate that the new zone lock is not taken
|
|
* as memory compaction should not move pages between nodes.
|
|
*/
|
|
page = pfn_to_page(low_pfn);
|
|
if (page_zone(page) != zone)
|
|
continue;
|
|
|
|
if (!valid_page)
|
|
valid_page = page;
|
|
|
|
/* If isolation recently failed, do not retry */
|
|
pageblock_nr = low_pfn >> pageblock_order;
|
|
if (!isolation_suitable(cc, page))
|
|
goto next_pageblock;
|
|
|
|
/* Skip if free */
|
|
if (PageBuddy(page))
|
|
continue;
|
|
|
|
/*
|
|
* For async migration, also only scan in MOVABLE blocks. Async
|
|
* migration is optimistic to see if the minimum amount of work
|
|
* satisfies the allocation
|
|
*/
|
|
if (!cc->sync && last_pageblock_nr != pageblock_nr &&
|
|
!migrate_async_suitable(get_pageblock_migratetype(page))) {
|
|
cc->finished_update_migrate = true;
|
|
goto next_pageblock;
|
|
}
|
|
|
|
/*
|
|
* 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 (locked && balloon_page_isolate(page)) {
|
|
/* Successfully isolated */
|
|
cc->finished_update_migrate = true;
|
|
list_add(&page->lru, migratelist);
|
|
cc->nr_migratepages++;
|
|
nr_isolated++;
|
|
goto check_compact_cluster;
|
|
}
|
|
}
|
|
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)
|
|
goto next_pageblock;
|
|
low_pfn += (1 << compound_order(page)) - 1;
|
|
continue;
|
|
}
|
|
|
|
/* Check if it is ok to still hold the lock */
|
|
locked = compact_checklock_irqsave(&zone->lru_lock, &flags,
|
|
locked, cc);
|
|
if (!locked || fatal_signal_pending(current))
|
|
break;
|
|
|
|
/* Recheck PageLRU and PageTransHuge under lock */
|
|
if (!PageLRU(page))
|
|
continue;
|
|
if (PageTransHuge(page)) {
|
|
low_pfn += (1 << compound_order(page)) - 1;
|
|
continue;
|
|
}
|
|
|
|
if (!cc->sync)
|
|
mode |= ISOLATE_ASYNC_MIGRATE;
|
|
|
|
if (unevictable)
|
|
mode |= ISOLATE_UNEVICTABLE;
|
|
|
|
lruvec = mem_cgroup_page_lruvec(page, zone);
|
|
|
|
/* Try isolate the page */
|
|
if (__isolate_lru_page(page, mode) != 0)
|
|
continue;
|
|
|
|
VM_BUG_ON(PageTransCompound(page));
|
|
|
|
/* Successfully isolated */
|
|
cc->finished_update_migrate = true;
|
|
del_page_from_lru_list(page, lruvec, page_lru(page));
|
|
list_add(&page->lru, migratelist);
|
|
cc->nr_migratepages++;
|
|
nr_isolated++;
|
|
|
|
check_compact_cluster:
|
|
/* Avoid isolating too much */
|
|
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) {
|
|
++low_pfn;
|
|
break;
|
|
}
|
|
|
|
continue;
|
|
|
|
next_pageblock:
|
|
low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1;
|
|
last_pageblock_nr = pageblock_nr;
|
|
}
|
|
|
|
acct_isolated(zone, locked, cc);
|
|
|
|
if (locked)
|
|
spin_unlock_irqrestore(&zone->lru_lock, flags);
|
|
|
|
/* Update the pageblock-skip if the whole pageblock was scanned */
|
|
if (low_pfn == end_pfn)
|
|
update_pageblock_skip(cc, valid_page, nr_isolated, true);
|
|
|
|
trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
|
|
|
|
count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned);
|
|
if (nr_isolated)
|
|
count_compact_events(COMPACTISOLATED, nr_isolated);
|
|
|
|
return low_pfn;
|
|
}
|
|
|
|
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
|
|
#ifdef CONFIG_COMPACTION
|
|
/*
|
|
* 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 zone *zone,
|
|
struct compact_control *cc)
|
|
{
|
|
struct page *page;
|
|
unsigned long high_pfn, low_pfn, pfn, z_end_pfn, end_pfn;
|
|
int nr_freepages = cc->nr_freepages;
|
|
struct list_head *freelist = &cc->freepages;
|
|
|
|
/*
|
|
* Initialise the free scanner. The starting point is where we last
|
|
* scanned from (or the end of the zone if starting). The low point
|
|
* is the end of the pageblock the migration scanner is using.
|
|
*/
|
|
pfn = cc->free_pfn;
|
|
low_pfn = cc->migrate_pfn + pageblock_nr_pages;
|
|
|
|
/*
|
|
* Take care that if the migration scanner is at the end of the zone
|
|
* that the free scanner does not accidentally move to the next zone
|
|
* in the next isolation cycle.
|
|
*/
|
|
high_pfn = min(low_pfn, pfn);
|
|
|
|
z_end_pfn = zone_end_pfn(zone);
|
|
|
|
/*
|
|
* 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 (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
|
|
pfn -= pageblock_nr_pages) {
|
|
unsigned long isolated;
|
|
|
|
/*
|
|
* This can iterate a massively long zone without finding any
|
|
* suitable migration targets, so periodically check if we need
|
|
* to schedule.
|
|
*/
|
|
cond_resched();
|
|
|
|
if (!pfn_valid(pfn))
|
|
continue;
|
|
|
|
/*
|
|
* Check for overlapping nodes/zones. 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.
|
|
*/
|
|
page = pfn_to_page(pfn);
|
|
if (page_zone(page) != zone)
|
|
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 */
|
|
isolated = 0;
|
|
|
|
/*
|
|
* As pfn may not start aligned, pfn+pageblock_nr_page
|
|
* may cross a MAX_ORDER_NR_PAGES boundary and miss
|
|
* a pfn_valid check. Ensure isolate_freepages_block()
|
|
* only scans within a pageblock
|
|
*/
|
|
end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
|
|
end_pfn = min(end_pfn, z_end_pfn);
|
|
isolated = isolate_freepages_block(cc, pfn, end_pfn,
|
|
freelist, false);
|
|
nr_freepages += isolated;
|
|
|
|
/*
|
|
* Record the highest PFN we isolated pages from. When next
|
|
* looking for free pages, the search will restart here as
|
|
* page migration may have returned some pages to the allocator
|
|
*/
|
|
if (isolated) {
|
|
cc->finished_update_free = true;
|
|
high_pfn = max(high_pfn, pfn);
|
|
}
|
|
}
|
|
|
|
/* split_free_page does not map the pages */
|
|
map_pages(freelist);
|
|
|
|
cc->free_pfn = high_pfn;
|
|
cc->nr_freepages = nr_freepages;
|
|
}
|
|
|
|
/*
|
|
* 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 */
|
|
if (list_empty(&cc->freepages)) {
|
|
isolate_freepages(cc->zone, 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;
|
|
}
|
|
|
|
/*
|
|
* We cannot control nr_migratepages and nr_freepages fully when migration is
|
|
* running as migrate_pages() has no knowledge of compact_control. When
|
|
* migration is complete, we count the number of pages on the lists by hand.
|
|
*/
|
|
static void update_nr_listpages(struct compact_control *cc)
|
|
{
|
|
int nr_migratepages = 0;
|
|
int nr_freepages = 0;
|
|
struct page *page;
|
|
|
|
list_for_each_entry(page, &cc->migratepages, lru)
|
|
nr_migratepages++;
|
|
list_for_each_entry(page, &cc->freepages, lru)
|
|
nr_freepages++;
|
|
|
|
cc->nr_migratepages = nr_migratepages;
|
|
cc->nr_freepages = 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;
|
|
|
|
/*
|
|
* Isolate all pages that can be migrated from the block pointed to by
|
|
* the migrate scanner within compact_control.
|
|
*/
|
|
static isolate_migrate_t isolate_migratepages(struct zone *zone,
|
|
struct compact_control *cc)
|
|
{
|
|
unsigned long low_pfn, end_pfn;
|
|
|
|
/* Do not scan outside zone boundaries */
|
|
low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
|
|
|
|
/* Only scan within a pageblock boundary */
|
|
end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages);
|
|
|
|
/* Do not cross the free scanner or scan within a memory hole */
|
|
if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
|
|
cc->migrate_pfn = end_pfn;
|
|
return ISOLATE_NONE;
|
|
}
|
|
|
|
/* Perform the isolation */
|
|
low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn, false);
|
|
if (!low_pfn || cc->contended)
|
|
return ISOLATE_ABORT;
|
|
|
|
cc->migrate_pfn = low_pfn;
|
|
|
|
return ISOLATE_SUCCESS;
|
|
}
|
|
|
|
static int compact_finished(struct zone *zone,
|
|
struct compact_control *cc)
|
|
{
|
|
unsigned int order;
|
|
unsigned long watermark;
|
|
|
|
if (fatal_signal_pending(current))
|
|
return COMPACT_PARTIAL;
|
|
|
|
/* Compaction run completes if the migrate and free scanner meet */
|
|
if (cc->free_pfn <= cc->migrate_pfn) {
|
|
/*
|
|
* 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);
|
|
watermark += (1 << cc->order);
|
|
|
|
if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
|
|
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];
|
|
|
|
/* Job done if page is free of the right migratetype */
|
|
if (!list_empty(&area->free_list[cc->migratetype]))
|
|
return COMPACT_PARTIAL;
|
|
|
|
/* Job done if allocation would set block type */
|
|
if (cc->order >= pageblock_order && area->nr_free)
|
|
return COMPACT_PARTIAL;
|
|
}
|
|
|
|
return COMPACT_CONTINUE;
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
*/
|
|
unsigned long compaction_suitable(struct zone *zone, int order)
|
|
{
|
|
int fragindex;
|
|
unsigned long watermark;
|
|
|
|
/*
|
|
* order == -1 is expected when compacting via
|
|
* /proc/sys/vm/compact_memory
|
|
*/
|
|
if (order == -1)
|
|
return COMPACT_CONTINUE;
|
|
|
|
/*
|
|
* 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 = low_wmark_pages(zone) + (2UL << order);
|
|
if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
|
|
return COMPACT_SKIPPED;
|
|
|
|
/*
|
|
* fragmentation index determines if allocation failures are due to
|
|
* low memory or external fragmentation
|
|
*
|
|
* index of -1000 implies allocations might succeed depending on
|
|
* watermarks
|
|
* 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_SKIPPED;
|
|
|
|
if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
|
|
0, 0))
|
|
return COMPACT_PARTIAL;
|
|
|
|
return COMPACT_CONTINUE;
|
|
}
|
|
|
|
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);
|
|
|
|
ret = compaction_suitable(zone, cc->order);
|
|
switch (ret) {
|
|
case COMPACT_PARTIAL:
|
|
case COMPACT_SKIPPED:
|
|
/* Compaction is likely to fail */
|
|
return ret;
|
|
case COMPACT_CONTINUE:
|
|
/* Fall through to compaction */
|
|
;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
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 = cc->migrate_pfn;
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
|
|
migrate_prep_local();
|
|
|
|
while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
|
|
unsigned long nr_migrate, nr_remaining;
|
|
int err;
|
|
|
|
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:
|
|
continue;
|
|
case ISOLATE_SUCCESS:
|
|
;
|
|
}
|
|
|
|
nr_migrate = cc->nr_migratepages;
|
|
err = migrate_pages(&cc->migratepages, compaction_alloc,
|
|
(unsigned long)cc,
|
|
cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC,
|
|
MR_COMPACTION);
|
|
update_nr_listpages(cc);
|
|
nr_remaining = cc->nr_migratepages;
|
|
|
|
trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
|
|
nr_remaining);
|
|
|
|
/* Release isolated pages not migrated */
|
|
if (err) {
|
|
putback_movable_pages(&cc->migratepages);
|
|
cc->nr_migratepages = 0;
|
|
if (err == -ENOMEM) {
|
|
ret = COMPACT_PARTIAL;
|
|
goto out;
|
|
}
|
|
}
|
|
}
|
|
|
|
out:
|
|
/* Release free pages and check accounting */
|
|
cc->nr_freepages -= release_freepages(&cc->freepages);
|
|
VM_BUG_ON(cc->nr_freepages != 0);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static unsigned long compact_zone_order(struct zone *zone,
|
|
int order, gfp_t gfp_mask,
|
|
bool sync, bool *contended)
|
|
{
|
|
unsigned long ret;
|
|
struct compact_control cc = {
|
|
.nr_freepages = 0,
|
|
.nr_migratepages = 0,
|
|
.order = order,
|
|
.migratetype = allocflags_to_migratetype(gfp_mask),
|
|
.zone = zone,
|
|
.sync = sync,
|
|
};
|
|
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
|
|
* @zonelist: The zonelist used for the current allocation
|
|
* @order: The order of the current allocation
|
|
* @gfp_mask: The GFP mask of the current allocation
|
|
* @nodemask: The allowed nodes to allocate from
|
|
* @sync: Whether migration is synchronous or not
|
|
* @contended: Return value that is true if compaction was aborted due to lock contention
|
|
* @page: Optionally capture a free page of the requested order during compaction
|
|
*
|
|
* This is the main entry point for direct page compaction.
|
|
*/
|
|
unsigned long try_to_compact_pages(struct zonelist *zonelist,
|
|
int order, gfp_t gfp_mask, nodemask_t *nodemask,
|
|
bool sync, bool *contended)
|
|
{
|
|
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
|
|
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_SKIPPED;
|
|
int alloc_flags = 0;
|
|
|
|
/* Check if the GFP flags allow compaction */
|
|
if (!order || !may_enter_fs || !may_perform_io)
|
|
return rc;
|
|
|
|
count_compact_event(COMPACTSTALL);
|
|
|
|
#ifdef CONFIG_CMA
|
|
if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
|
|
alloc_flags |= ALLOC_CMA;
|
|
#endif
|
|
/* Compact each zone in the list */
|
|
for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
|
|
nodemask) {
|
|
int status;
|
|
|
|
status = compact_zone_order(zone, order, gfp_mask, sync,
|
|
contended);
|
|
rc = max(status, rc);
|
|
|
|
/* If a normal allocation would succeed, stop compacting */
|
|
if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0,
|
|
alloc_flags))
|
|
break;
|
|
}
|
|
|
|
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);
|
|
|
|
if (cc->order == -1 || !compaction_deferred(zone, cc->order))
|
|
compact_zone(zone, cc);
|
|
|
|
if (cc->order > 0) {
|
|
int ok = zone_watermark_ok(zone, cc->order,
|
|
low_wmark_pages(zone), 0, 0);
|
|
if (ok && cc->order >= zone->compact_order_failed)
|
|
zone->compact_order_failed = cc->order + 1;
|
|
/* Currently async compaction is never deferred. */
|
|
else if (!ok && cc->sync)
|
|
defer_compaction(zone, cc->order);
|
|
}
|
|
|
|
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,
|
|
.sync = false,
|
|
};
|
|
|
|
if (!order)
|
|
return;
|
|
|
|
__compact_pgdat(pgdat, &cc);
|
|
}
|
|
|
|
static void compact_node(int nid)
|
|
{
|
|
struct compact_control cc = {
|
|
.order = -1,
|
|
.sync = 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)
|
|
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 */
|