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From: David Rientjes <rientjes@google.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip
Date: Mon, 11 Sep 2017 14:13:36 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1709111411520.108216@chino.kir.corp.google.com> (raw)
In-Reply-To: <c4a19acf-20f7-095a-1234-926b8d98c174@suse.cz>

On Mon, 11 Sep 2017, Vlastimil Babka wrote:

> > A follow-up change will set the pageblock skip for this memory since it is 
> > never useful for either scanner.
> > """
> > 
> >> Also there's now a danger that in cases where there's no direct
> >> compaction happening (just kcompactd), nothing will ever call
> >> __reset_isolation_suitable().
> >>
> > 
> > I'm not sure that is helpful in a context where no high-order memory can 
> > call direct compaction that kcompactd needlessly scanning the same memory 
> > over and over is beneficial.
> 
> The point is that if it becomes beneficial again, we won't know as there
> will be still be skip bits.
> 

Why is kcompactd_do_work() not sometimes doing 
__reset_isolation_suitable() in the first place, if only to reset the 
per-zone migration and freeing scanner cached pfns?  It seems fragile to 
rely on other threads doing direct compaction to reset the per-zone state 
of compaction.

WARNING: multiple messages have this Message-ID (diff)
From: David Rientjes <rientjes@google.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip
Date: Mon, 11 Sep 2017 14:13:36 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1709111411520.108216@chino.kir.corp.google.com> (raw)
In-Reply-To: <c4a19acf-20f7-095a-1234-926b8d98c174@suse.cz>

On Mon, 11 Sep 2017, Vlastimil Babka wrote:

> > A follow-up change will set the pageblock skip for this memory since it is 
> > never useful for either scanner.
> > """
> > 
> >> Also there's now a danger that in cases where there's no direct
> >> compaction happening (just kcompactd), nothing will ever call
> >> __reset_isolation_suitable().
> >>
> > 
> > I'm not sure that is helpful in a context where no high-order memory can 
> > call direct compaction that kcompactd needlessly scanning the same memory 
> > over and over is beneficial.
> 
> The point is that if it becomes beneficial again, we won't know as there
> will be still be skip bits.
> 

Why is kcompactd_do_work() not sometimes doing 
__reset_isolation_suitable() in the first place, if only to reset the 
per-zone migration and freeing scanner cached pfns?  It seems fragile to 
rely on other threads doing direct compaction to reset the per-zone state 
of compaction.

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  reply	other threads:[~2017-09-11 21:13 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-15 23:39 [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip David Rientjes
2017-08-15 23:39 ` David Rientjes
2017-08-15 23:39 ` [patch 2/2] mm, compaction: persistently skip hugetlbfs pageblocks David Rientjes
2017-08-15 23:39   ` David Rientjes
2017-08-18  8:49   ` Michal Hocko
2017-08-18  8:49     ` Michal Hocko
2017-08-21  0:36     ` [patch -mm] mm, compaction: persistently skip hugetlbfs pageblocks fix David Rientjes
2017-08-21  0:36       ` David Rientjes
2017-08-21  6:37       ` Michal Hocko
2017-08-21  6:37         ` Michal Hocko
2017-08-23  8:41   ` [patch 2/2] mm, compaction: persistently skip hugetlbfs pageblocks Vlastimil Babka
2017-08-23  8:41     ` Vlastimil Babka
2017-09-01 12:32     ` Vlastimil Babka
2017-09-01 12:32       ` Vlastimil Babka
2017-09-11  1:13       ` David Rientjes
2017-09-11  1:13         ` David Rientjes
2017-09-11  1:12     ` David Rientjes
2017-09-11  1:12       ` David Rientjes
2017-09-11  6:50       ` Vlastimil Babka
2017-09-11  6:50         ` Vlastimil Babka
2017-09-11 21:11         ` David Rientjes
2017-09-11 21:11           ` David Rientjes
2017-08-23  8:23 ` [patch 1/2] mm, compaction: kcompactd should not ignore pageblock skip Vlastimil Babka
2017-08-23  8:23   ` Vlastimil Babka
2017-09-11  1:07   ` David Rientjes
2017-09-11  1:07     ` David Rientjes
2017-09-11  6:34     ` Vlastimil Babka
2017-09-11  6:34       ` Vlastimil Babka
2017-09-11 21:13       ` David Rientjes [this message]
2017-09-11 21:13         ` David Rientjes

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