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![Joonsoo Kim](/assets/img/avatar_default.png)
We cache isolate_start_pfn before entering isolate_migratepages(). If pageblock is skipped in isolate_migratepages() due to whatever reason, cc->migrate_pfn can be far from isolate_start_pfn hence we flush pages that were freed. For example, the following scenario can be possible: - assume order-9 compaction, pageblock order is 9 - start_isolate_pfn is 0x200 - isolate_migratepages() - skip a number of pageblocks - start to isolate from pfn 0x600 - cc->migrate_pfn = 0x620 - return - last_migrated_pfn is set to 0x200 - check flushing condition - current_block_start is set to 0x600 - last_migrated_pfn < current_block_start then do useless flush This wrong flush would not help the performance and success rate so this patch tries to fix it. One simple way to know the exact position where we start to isolate migratable pages is that we cache it in isolate_migratepages() before entering actual isolation. This patch implements that and fixes the problem. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1764 lines
48 KiB
C
1764 lines
48 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 <linux/kasan.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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#ifdef CONFIG_TRACEPOINTS
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static const char *const compaction_status_string[] = {
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"deferred",
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"skipped",
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"continue",
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"partial",
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"complete",
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"no_suitable_page",
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"not_suitable_zone",
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};
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#endif
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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 high_pfn = 0;
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list_for_each_entry_safe(page, next, freelist, lru) {
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unsigned long pfn = page_to_pfn(page);
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list_del(&page->lru);
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__free_page(page);
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if (pfn > high_pfn)
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high_pfn = pfn;
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}
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return high_pfn;
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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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kasan_alloc_pages(page, 0);
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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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/*
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* Check that the whole (or subset of) a pageblock given by the interval of
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* [start_pfn, end_pfn) is valid and within the same zone, before scanning it
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* with the migration of free compaction scanner. The scanners then need to
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* use only pfn_valid_within() check for arches that allow holes within
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* pageblocks.
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*
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* Return struct page pointer of start_pfn, or NULL if checks were not passed.
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*
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* It's possible on some configurations to have a setup like node0 node1 node0
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* i.e. it's possible that all pages within a zones range of pages do not
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* belong to a single zone. We assume that a border between node0 and node1
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* can occur within a single pageblock, but not a node0 node1 node0
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* interleaving within a single pageblock. It is therefore sufficient to check
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* the first and last page of a pageblock and avoid checking each individual
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* page in a pageblock.
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*/
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static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
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unsigned long end_pfn, struct zone *zone)
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{
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struct page *start_page;
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struct page *end_page;
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/* end_pfn is one past the range we are checking */
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end_pfn--;
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if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
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return NULL;
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start_page = pfn_to_page(start_pfn);
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if (page_zone(start_page) != zone)
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return NULL;
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end_page = pfn_to_page(end_pfn);
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/* This gives a shorter code than deriving page_zone(end_page) */
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if (page_zone_id(start_page) != page_zone_id(end_page))
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return NULL;
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return start_page;
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}
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#ifdef CONFIG_COMPACTION
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/* Do not skip compaction more than 64 times */
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#define COMPACT_MAX_DEFER_SHIFT 6
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/*
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* Compaction is deferred when compaction fails to result in a page
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* allocation success. 1 << compact_defer_limit compactions are skipped up
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* to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
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*/
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void defer_compaction(struct zone *zone, int order)
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{
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zone->compact_considered = 0;
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zone->compact_defer_shift++;
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if (order < zone->compact_order_failed)
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zone->compact_order_failed = order;
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if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
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zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
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trace_mm_compaction_defer_compaction(zone, order);
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}
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/* Returns true if compaction should be skipped this time */
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bool compaction_deferred(struct zone *zone, int order)
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{
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unsigned long defer_limit = 1UL << zone->compact_defer_shift;
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if (order < zone->compact_order_failed)
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return false;
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/* Avoid possible overflow */
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if (++zone->compact_considered > defer_limit)
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zone->compact_considered = defer_limit;
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if (zone->compact_considered >= defer_limit)
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return false;
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trace_mm_compaction_deferred(zone, order);
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return true;
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}
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/*
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* Update defer tracking counters after successful compaction of given order,
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* which means an allocation either succeeded (alloc_success == true) or is
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* expected to succeed.
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*/
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void compaction_defer_reset(struct zone *zone, int order,
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bool alloc_success)
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{
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if (alloc_success) {
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zone->compact_considered = 0;
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zone->compact_defer_shift = 0;
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}
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if (order >= zone->compact_order_failed)
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zone->compact_order_failed = order + 1;
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trace_mm_compaction_defer_reset(zone, order);
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}
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/* Returns true if restarting compaction after many failures */
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bool compaction_restarting(struct zone *zone, int order)
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{
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if (order < zone->compact_order_failed)
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return false;
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return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
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zone->compact_considered >= 1UL << zone->compact_defer_shift;
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}
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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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static void reset_cached_positions(struct zone *zone)
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{
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zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
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zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
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zone->compact_cached_free_pfn = zone_end_pfn(zone);
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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_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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reset_cached_positions(zone);
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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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unsigned long pfn;
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if (cc->ignore_skip_hint)
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return;
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if (!page)
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return;
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if (nr_isolated)
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return;
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set_pageblock_skip(page);
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pfn = page_to_pfn(page);
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/* Update where async and sync compaction should restart */
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if (migrate_scanner) {
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if (pfn > zone->compact_cached_migrate_pfn[0])
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zone->compact_cached_migrate_pfn[0] = pfn;
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if (cc->mode != MIGRATE_ASYNC &&
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pfn > zone->compact_cached_migrate_pfn[1])
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zone->compact_cached_migrate_pfn[1] = pfn;
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} else {
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if (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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#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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/*
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* Compaction requires the taking of some coarse locks that are potentially
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* very heavily contended. For async compaction, back out if the lock cannot
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* be taken immediately. For sync compaction, spin on the lock if needed.
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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 not held and compaction should abort
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*/
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static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags,
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struct compact_control *cc)
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{
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if (cc->mode == MIGRATE_ASYNC) {
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if (!spin_trylock_irqsave(lock, *flags)) {
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cc->contended = COMPACT_CONTENDED_LOCK;
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return false;
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}
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} else {
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spin_lock_irqsave(lock, *flags);
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}
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return true;
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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. The lock should be periodically unlocked to avoid
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* having disabled IRQs for a long time, even when there is nobody waiting on
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* the lock. It might also be that allowing the IRQs will result in
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* need_resched() becoming true. If scheduling is needed, async compaction
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* aborts. Sync compaction schedules.
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* Either compaction type will also abort if a fatal signal is pending.
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* In either case if the lock was locked, it is dropped and not regained.
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*
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* Returns true if compaction should abort due to fatal signal pending, or
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* async compaction due to need_resched()
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* Returns false when compaction can continue (sync compaction might have
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* scheduled)
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*/
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static bool compact_unlock_should_abort(spinlock_t *lock,
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unsigned long flags, bool *locked, struct compact_control *cc)
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{
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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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if (fatal_signal_pending(current)) {
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cc->contended = COMPACT_CONTENDED_SCHED;
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return true;
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}
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|
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if (need_resched()) {
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if (cc->mode == MIGRATE_ASYNC) {
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cc->contended = COMPACT_CONTENDED_SCHED;
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return true;
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}
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cond_resched();
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}
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return false;
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}
|
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|
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/*
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* Aside from avoiding lock contention, compaction also periodically checks
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* need_resched() and either schedules in sync compaction or aborts async
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* compaction. This is similar to what compact_unlock_should_abort() does, but
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* is used where no lock is concerned.
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*
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* Returns false when no scheduling was needed, or sync compaction scheduled.
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* Returns true when async compaction should abort.
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*/
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static inline bool compact_should_abort(struct compact_control *cc)
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{
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/* async compaction aborts if contended */
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if (need_resched()) {
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if (cc->mode == MIGRATE_ASYNC) {
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cc->contended = COMPACT_CONTENDED_SCHED;
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return true;
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}
|
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cond_resched();
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}
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return false;
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}
|
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|
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/*
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* Isolate free pages onto a private freelist. If @strict is true, will abort
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* returning 0 on any invalid PFNs or non-free pages inside of the pageblock
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* (even though it may still end up isolating 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 *start_pfn,
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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 flags = 0;
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bool locked = false;
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unsigned long blockpfn = *start_pfn;
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cursor = pfn_to_page(blockpfn);
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|
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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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|
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/*
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* Periodically drop the lock (if held) regardless of its
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* contention, to give chance to IRQs. Abort if fatal signal
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* pending or async compaction detects need_resched()
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*/
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if (!(blockpfn % SWAP_CLUSTER_MAX)
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&& compact_unlock_should_abort(&cc->zone->lock, flags,
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&locked, cc))
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break;
|
|
|
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nr_scanned++;
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if (!pfn_valid_within(blockpfn))
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goto isolate_fail;
|
|
|
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if (!valid_page)
|
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valid_page = page;
|
|
|
|
/*
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* For compound pages such as THP and hugetlbfs, we can save
|
|
* potentially a lot of iterations if we skip them at once.
|
|
* The check is racy, but we can consider only valid values
|
|
* and the only danger is skipping too much.
|
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*/
|
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if (PageCompound(page)) {
|
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unsigned int comp_order = compound_order(page);
|
|
|
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if (likely(comp_order < MAX_ORDER)) {
|
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blockpfn += (1UL << comp_order) - 1;
|
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cursor += (1UL << comp_order) - 1;
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}
|
|
|
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goto isolate_fail;
|
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}
|
|
|
|
if (!PageBuddy(page))
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|
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)
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|
break;
|
|
|
|
/* Recheck this is a buddy page under lock */
|
|
if (!PageBuddy(page))
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|
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;
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|
continue;
|
|
}
|
|
|
|
isolate_fail:
|
|
if (strict)
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|
break;
|
|
else
|
|
continue;
|
|
|
|
}
|
|
|
|
/*
|
|
* There is a tiny chance that we have read bogus compound_order(),
|
|
* so be careful to not go outside of the pageblock.
|
|
*/
|
|
if (unlikely(blockpfn > end_pfn))
|
|
blockpfn = end_pfn;
|
|
|
|
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++) {
|
|
bool is_lru;
|
|
|
|
/*
|
|
* 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
|
|
*/
|
|
is_lru = PageLRU(page);
|
|
if (!is_lru) {
|
|
if (unlikely(balloon_page_movable(page))) {
|
|
if (balloon_page_isolate(page)) {
|
|
/* Successfully isolated */
|
|
goto isolate_success;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Regardless of being on LRU, compound pages such as THP and
|
|
* hugetlbfs are not to be compacted. We can potentially save
|
|
* a lot of iterations if we skip them at once. The check is
|
|
* racy, but we can consider only valid values and the only
|
|
* danger is skipping too much.
|
|
*/
|
|
if (PageCompound(page)) {
|
|
unsigned int comp_order = compound_order(page);
|
|
|
|
if (likely(comp_order < MAX_ORDER))
|
|
low_pfn += (1UL << comp_order) - 1;
|
|
|
|
continue;
|
|
}
|
|
|
|
if (!is_lru)
|
|
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 PageCompound under lock */
|
|
if (!PageLRU(page))
|
|
continue;
|
|
|
|
/*
|
|
* Page become compound since the non-locked check,
|
|
* and it's on LRU. It can only be a THP so the order
|
|
* is safe to read and it's 0 for tail pages.
|
|
*/
|
|
if (unlikely(PageCompound(page))) {
|
|
low_pfn += (1UL << 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(PageCompound(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;
|
|
}
|
|
|
|
/*
|
|
* Test whether the free scanner has reached the same or lower pageblock than
|
|
* the migration scanner, and compaction should thus terminate.
|
|
*/
|
|
static inline bool compact_scanners_met(struct compact_control *cc)
|
|
{
|
|
return (cc->free_pfn >> pageblock_order)
|
|
<= (cc->migrate_pfn >> pageblock_order);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
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);
|
|
|
|
/*
|
|
* If we isolated enough freepages, or aborted due to async
|
|
* compaction being contended, terminate the loop.
|
|
* 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.
|
|
*/
|
|
if ((cc->nr_freepages >= cc->nr_migratepages)
|
|
|| cc->contended) {
|
|
if (isolate_start_pfn >= block_end_pfn)
|
|
isolate_start_pfn =
|
|
block_start_pfn - pageblock_nr_pages;
|
|
break;
|
|
} else {
|
|
/*
|
|
* isolate_freepages_block() should not terminate
|
|
* prematurely unless contended, or isolated enough
|
|
*/
|
|
VM_BUG_ON(isolate_start_pfn < block_end_pfn);
|
|
}
|
|
}
|
|
|
|
/* split_free_page does not map the pages */
|
|
map_pages(freelist);
|
|
|
|
/*
|
|
* Record where the free scanner will restart next time. Either we
|
|
* broke from the loop and set isolate_start_pfn based on the last
|
|
* call to isolate_freepages_block(), or we met the migration scanner
|
|
* and the loop terminated due to isolate_start_pfn < low_pfn
|
|
*/
|
|
cc->free_pfn = isolate_start_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;
|
|
unsigned long isolate_start_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 */
|
|
isolate_start_pfn = low_pfn;
|
|
low_pfn = isolate_migratepages_block(cc, low_pfn, end_pfn,
|
|
isolate_mode);
|
|
|
|
if (!low_pfn || cc->contended) {
|
|
acct_isolated(zone, cc);
|
|
return ISOLATE_ABORT;
|
|
}
|
|
|
|
/*
|
|
* Record where we could have freed pages by migration and not
|
|
* yet flushed them to buddy allocator.
|
|
* - this is the lowest page that could have been isolated and
|
|
* then freed by migration.
|
|
*/
|
|
if (cc->nr_migratepages && !cc->last_migrated_pfn)
|
|
cc->last_migrated_pfn = isolate_start_pfn;
|
|
|
|
/*
|
|
* 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. */
|
|
cc->migrate_pfn = low_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 (compact_scanners_met(cc)) {
|
|
/* Let the next compaction start anew. */
|
|
reset_cached_positions(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;
|
|
|
|
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;
|
|
}
|
|
cc->last_migrated_pfn = 0;
|
|
|
|
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;
|
|
|
|
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 && !compact_scanners_met(cc)) {
|
|
ret = COMPACT_PARTIAL;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
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 && cc->last_migrated_pfn) {
|
|
int cpu;
|
|
unsigned long current_block_start =
|
|
cc->migrate_pfn & ~((1UL << cc->order) - 1);
|
|
|
|
if (cc->last_migrated_pfn < current_block_start) {
|
|
cpu = get_cpu();
|
|
lru_add_drain_cpu(cpu);
|
|
drain_local_pages(zone);
|
|
put_cpu();
|
|
/* No more flushing until we migrate again */
|
|
cc->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 */
|