linux-kernel - Re: [patch] mm, compaction: drain pcps for zone when kcompactd fails

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Message-ID: <alpine.DEB.2.20.1803011535280.173043@chino.kir.corp.google.com>
Date:   Thu, 1 Mar 2018 15:38:08 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, compaction: drain pcps for zone when kcompactd
 fails

On Thu, 1 Mar 2018, Andrew Morton wrote:

> On Thu, 1 Mar 2018 03:42:04 -0800 (PST) David Rientjes <rientjes@...gle.com> wrote:
> 
> > It's possible for buddy pages to become stranded on pcps that, if drained,
> > could be merged with other buddy pages on the zone's free area to form
> > large order pages, including up to MAX_ORDER.
> 
> I grabbed this as-is.  Perhaps you could send along a new changelog so
> that others won't be asking the same questions as Vlastimil?
> 
> The patch has no reviews or acks at this time...
> 

Thanks.

As mentioned in my response to Vlastimil, I think the case could also be 
made that we should do drain_all_pages(zone) in try_to_compact_pages() 
when we defer for direct compactors.  It would be great to have feedback 
from those on the cc on that point, the patch in general, and then I can 
send an update.