From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Rik van Riel <riel@redhat.com>,
David Rientjes <rientjes@google.com>,
Minchan Kim <minchan@kernel.org>, Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH v2 4/4] mm, compaction: direct freepage allocation for async direct compaction
Date: Mon, 4 Apr 2016 13:05:19 +0200 [thread overview]
Message-ID: <57024A6F.100@suse.cz> (raw)
In-Reply-To: <20160404093159.GB4773@techsingularity.net>
On 04/04/2016 11:31 AM, Mel Gorman 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.
>>
>
> What prevents the free pages being allocated from behind the migration
> scanner? Having compaction abort when the scanners meet misses
> compaction opportunities but it avoids the problem of Compactor A using
> pageblock X as a migration target and Compactor B using pageblock X as a
> migration source.
It's true that there's no complete protection, but parallel async
compactions should eventually get detect contention and back off. Sync
compaction keeps using the free scanner, so this seemed like a safe
thing to attempt in the initial async compaction, without compromising
success rates thanks to the followup sync compaction.
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next prev parent reply other threads:[~2016-04-04 11:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-31 8:50 [PATCH v2 0/4] reduce latency of direct async compaction Vlastimil Babka
2016-03-31 8:50 ` [PATCH v2 1/4] mm, compaction: wrap calculating first and last pfn of pageblock Vlastimil Babka
2016-03-31 8:50 ` [PATCH v2 2/4] mm, compaction: reduce spurious pcplist drains Vlastimil Babka
2016-03-31 8:50 ` [PATCH v2 3/4] mm, compaction: skip blocks where isolation fails in async direct compaction Vlastimil Babka
2016-03-31 8:50 ` [PATCH v2 4/4] mm, compaction: direct freepage allocation for " Vlastimil Babka
2016-04-04 9:31 ` Mel Gorman
2016-04-04 11:05 ` Vlastimil Babka [this message]
2016-04-11 7:13 ` Joonsoo Kim
2016-04-11 7:27 ` Vlastimil Babka
2016-04-11 7:05 ` [PATCH v2 0/4] reduce latency of direct async compaction Joonsoo Kim
2016-04-11 8:17 ` Vlastimil Babka
2016-04-12 4:49 ` Joonsoo Kim
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