linux-kernel - Re: [PATCH 2/2] mm/page_alloc: fix never set ALLOC

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Message-ID: <20190424234052.GW18914@techsingularity.net>
Date:   Thu, 25 Apr 2019 00:40:53 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm/page_alloc: fix never set ALLOC_NOFRAGMENT flag

On Wed, Apr 24, 2019 at 03:46:24PM -0700, Andrew Morton wrote:
> On Wed, 24 Apr 2019 10:04:03 +0100 Mel Gorman <mgorman@...hsingularity.net> wrote:
> 
> > On Tue, Apr 23, 2019 at 12:01:43PM -0700, Andrew Morton wrote:
> > > On Tue, 23 Apr 2019 15:08:06 +0300 Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
> > > 
> > > > Commit 0a79cdad5eb2 ("mm: use alloc_flags to record if kswapd can wake")
> > > > removed setting of the ALLOC_NOFRAGMENT flag. Bring it back.
> > > 
> > > What are the runtime effects of this fix?
> > 
> > The runtime effect is that ALLOC_NOFRAGMENT behaviour is restored so
> > that allocations are spread across local zones to avoid fragmentation
> > due to mixing pageblocks as long as possible.
> 
> OK, thanks.  Is this worth a -stable backport?

Yes, but only for 5.0 obviously and both should be included if that is
the case. I did not push for it initially as problems in this area are
hard for a general user to detect and people have not complained about
5.0's fragmentation handling.

-- 
Mel Gorman
SUSE Labs