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Date: Thu, 2 Nov 2017 13:09:43 +0000 From: Mel Gorman <mgorman@...hsingularity.net> To: Vlastimil Babka <vbabka@...e.cz> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com> Subject: Re: [PATCH 2/3] mm, compaction: split off flag for not updating skip hints On Thu, Nov 02, 2017 at 01:17:05PM +0100, Vlastimil Babka wrote: > Pageblock skip hints were added as a heuristic for compaction, which shares > core code with CMA. Since CMA reliability would suffer from the heuristics, > compact_control flag ignore_skip_hint was added for the CMA use case. > Since commit 6815bf3f233e ("mm/compaction: respect ignore_skip_hint in > update_pageblock_skip") the flag also means that CMA won't *update* the skip > hints in addition to ignoring them. > > Today, direct compaction can also ignore the skip hints in the last resort > attempt, but there's no reason not to set them when isolation fails in such > case. Thus, this patch splits off a new no_set_skip_hint flag to avoid the > updating, which only CMA sets. This should improve the heuristics a bit, and > allow us to simplify the persistent skip bit handling as the next step. > > Signed-off-by: Vlastimil Babka <vbabka@...e.cz> Acked-by: Mel Gorman <mgorman@...hsingularity.net> -- Mel Gorman SUSE Labs
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