linux-kernel - Re: [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY

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Date:   Thu, 25 Jul 2019 09:06:31 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY_PRIORITY
 everywhere for costly orders

On Wed, Jul 24, 2019 at 10:50:13AM -0700, Mike Kravetz wrote:
> For PAGE_ALLOC_COSTLY_ORDER allocations, MIN_COMPACT_COSTLY_PRIORITY is
> minimum (highest priority).  Other places in the compaction code key off
> of MIN_COMPACT_PRIORITY.  Costly order allocations will never get to
> MIN_COMPACT_PRIORITY.  Therefore, some conditions will never be met for
> costly order allocations.
> 
> This was observed when hugetlb allocations could stall for minutes or
> hours when should_compact_retry() would return true more often then it
> should.  Specifically, this was in the case where compact_result was
> COMPACT_DEFERRED and COMPACT_PARTIAL_SKIPPED and no progress was being
> made.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs