linux-kernel - Re: [PATCH 11/11] mm: consider compaction feedback also for costly allocation

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Date:	Mon, 11 Apr 2016 17:07:15 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Joonsoo Kim <js1304@...il.com>,
	Hillf Danton <hillf.zj@...baba-inc.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 11/11] mm: consider compaction feedback also for costly
 allocation

On 04/05/2016 01:25 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> PAGE_ALLOC_COSTLY_ORDER retry logic is mostly handled inside
> should_reclaim_retry currently where we decide to not retry after at
> least order worth of pages were reclaimed or the watermark check for at
> least one zone would succeed after reclaiming all pages if the reclaim
> hasn't made any progress. Compaction feedback is mostly ignored and we
> just try to make sure that the compaction did at least something before
> giving up.
>
> The first condition was added by a41f24ea9fd6 ("page allocator: smarter
> retry of costly-order allocations) and it assumed that lumpy reclaim
> could have created a page of the sufficient order. Lumpy reclaim,
> has been removed quite some time ago so the assumption doesn't hold
> anymore. Remove the check for the number of reclaimed pages and rely
> on the compaction feedback solely. should_reclaim_retry now only
> makes sure that we keep retrying reclaim for high order pages only
> if they are hidden by watermaks so order-0 reclaim makes really sense.
>
> should_compact_retry now keeps retrying even for the costly allocations.
> The number of retries is reduced wrt. !costly requests because they are
> less important and harder to grant and so their pressure shouldn't cause
> contention for other requests or cause an over reclaim. We also do not
> reset no_progress_loops for costly request to make sure we do not keep
> reclaiming too agressively.

[...]

> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>