linux-kernel - Re: [PATCH v2 4/4] mm, compaction: direct freepage allocation for async direct compaction

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Message-ID: <570B51C6.4050005@suse.cz>
Date:	Mon, 11 Apr 2016 09:27:02 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...hsingularity.net>,
	Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v2 4/4] mm, compaction: direct freepage allocation for
 async direct compaction

On 04/11/2016 09:13 AM, Joonsoo Kim wrote:
> On Thu, Mar 31, 2016 at 10:50:36AM +0200, Vlastimil Babka wrote:
>> The goal of direct compaction is to quickly make a high-order page available
>> for the pending allocation. The free page scanner can add significant latency
>> when searching for migration targets, although to succeed the compaction, the
>> only important limit on the target free pages is that they must not come from
>> the same order-aligned block as the migrated pages.
>
> If we fails migration, free pages will remain and they can interfere
> further compaction success because they doesn't come from previous
> order-aligned block but can come from next order-aligned block. You
> need to free remaining freelist after migration attempt fails?

Oh, good point, thanks!