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Commit feeb6c80 authored by Charan Teja Reddy's avatar Charan Teja Reddy Committed by Gerrit - the friendly Code Review server
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mm: ignore the boosting of watermark under lowmemory 



When low on free memory and a fragmentation event at the same time
will cause the zone watermarks to be offsetted by watermark_boost
which in default is 150% of high watermark. The side effects of this
is the time taken by the reclaim to reach that level and thus the
subsequent reset of the watermark_boost can be higher and hence
killing of the FG tasks can happen in that time frame despite
the free memory is above zone->_watermark[WMARK_HIGH]. Ignore
boosting of watermark under this condition and thus we can create
more memory headroom.

Change-Id: Ia1fa5d766eee851ad3456f41b4b2d623cf4eeee3
Signed-off-by: default avatarCharan Teja Reddy <charante@codeaurora.org>
parent 4b832ee1

mm/page_alloc.c

+27 −1
Original line number Diff line number Diff line
@@ -2224,11 +2224,37 @@ static bool can_steal_fallback(unsigned int order, int start_mt) 
	return false;

}



static bool boost_eligible(struct zone *z)

{

	unsigned long high_wmark, threshold;

	unsigned long reclaim_eligible, free_pages;



	high_wmark = z->_watermark[WMARK_HIGH];

	reclaim_eligible = zone_page_state_snapshot(z, NR_ZONE_INACTIVE_FILE) +

			zone_page_state_snapshot(z, NR_ZONE_ACTIVE_FILE);

	free_pages = zone_page_state(z, NR_FREE_PAGES);

	threshold = high_wmark + (2 * mult_frac(high_wmark,

					watermark_boost_factor, 10000));



	/*

	 * Don't boost watermark If we are already low on memory where the

	 * boosting can simply put the watermarks at higher levels for a

	 * longer duration of time and thus the other users relied on the

	 * watermarks are forced to choose unintended decissions. If memory

	 * is so low, kswapd in normal mode should help.

	 */



	if (reclaim_eligible < threshold && free_pages < threshold)

		return false;



	return true;

}



static inline void boost_watermark(struct zone *zone)

{

	unsigned long max_boost;



	if (!watermark_boost_factor)

	if (!watermark_boost_factor || !boost_eligible(zone))

		return;



	max_boost = mult_frac(zone->_watermark[WMARK_HIGH],