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Commit 21015dfb authored by Vinayak Menon's avatar Vinayak Menon
Browse files

mm: compaction: fix the page state calculation in too_many_isolated 



Commit "mm: vmscan: fix the page state calculation in too_many_isolated"
fixed an issue where a number of tasks were blocked in reclaim path
for seconds, because of vmstat_diff not being synced in time.
A similar problem can happen in isolate_migratepages_block, where
similar calculation is performed. This patch fixes that.

Change-Id: Ie74f108ef770da688017b515fe37faea6f384589
Signed-off-by: default avatarVinayak Menon <vinmenon@codeaurora.org>
parent 1b92facc

mm/compaction.c

+34 −9
Original line number Diff line number Diff line
@@ -541,21 +541,46 @@ static void acct_isolated(struct zone *zone, struct compact_control *cc) 
	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)

static bool __too_many_isolated(struct zone *zone, int safe)

{

	unsigned long active, inactive, isolated;



	if (safe) {

		inactive = zone_page_state_snapshot(zone, NR_INACTIVE_FILE) +

			zone_page_state_snapshot(zone, NR_INACTIVE_ANON);

		active = zone_page_state_snapshot(zone, NR_ACTIVE_FILE) +

			zone_page_state_snapshot(zone, NR_ACTIVE_ANON);

		isolated = zone_page_state_snapshot(zone, NR_ISOLATED_FILE) +

			zone_page_state_snapshot(zone, NR_ISOLATED_ANON);

	} else {

		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;

}



/* Similar to reclaim, but different enough that they don't share logic */

static bool too_many_isolated(struct compact_control *cc)

{

	/*

	 * __too_many_isolated(safe=0) is fast but inaccurate, because it

	 * doesn't account for the vm_stat_diff[] counters.  So if it looks

	 * like too_many_isolated() is about to return true, fall back to the

	 * slower, more accurate zone_page_state_snapshot().

	 */

	if (unlikely(__too_many_isolated(cc->zone, 0))) {

		if (cc->mode != MIGRATE_ASYNC)

			return __too_many_isolated(cc->zone, 1);

	}



	return false;

}



/**

 * isolate_migratepages_block() - isolate all migrate-able pages within

 *				  a single pageblock
@@ -591,7 +616,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 
	 * 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))) {

	while (unlikely(too_many_isolated(cc))) {

		/* async migration should just abort */

		if (cc->mode == MIGRATE_ASYNC)

			return 0;