From: Mel Gorman <mgorman@techsingularity.net>
To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: 'Andrew Morton' <akpm@linux-foundation.org>,
'Johannes Weiner' <hannes@cmpxchg.org>,
'Vlastimil Babka' <vbabka@suse.cz>,
'linux-kernel' <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH] mm, vmscan: Give up balancing node for high order allocations earlier
Date: Tue, 12 Jul 2016 09:33:42 +0100 [thread overview]
Message-ID: <20160712083342.GC9806@techsingularity.net> (raw)
In-Reply-To: <013d01d1dc07$33896860$9a9c3920$@alibaba-inc.com>
On Tue, Jul 12, 2016 at 02:32:45PM +0800, Hillf Danton wrote:
> > > To avoid excessive reclaim, we give up rebalancing for high order
> > > allocations right after reclaiming enough pages.
> >
> > hm. What are the observed runtime effects of this change? Any testing
> > results?
> >
> This work was based on Mel's work, Sir,
> "[PATCH 00/27] Move LRU page reclaim from zones to nodes v7".
>
I believe Andrew understands that but the question is what is the
observed runtime effect of the patch?
> In "[PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes",
> fragmentation detection is introduced to avoid excessive reclaim. We bail
> out of balancing for high-order allocations if the pages reclaimed at the
> __current__ reclaim priority are two times more than required.
>
> In this work we give up reclaiming for high-order allocations if the
> __total__ number of pages reclaimed, from the first priority to the
> current priority, is more than needed, and in net result we reclaim less
> pages.
>
While it's clear what it does, it is not clear if it is an improvement. I had
read the patch, considered merging it and decided against it. This decision
was based on the fact the series did not appear to be over-reclaiming for
high-order pages when compared with zone-lru.
Did you test this patch with a workload that requires a lot of high-order
pages and see if kswapd was over-reclaiming and that this patch addressed
the issue?
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2016-07-12 8:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-29 5:42 [PATCH] mm, vmscan: Give up balancing node for high order allocations earlier Hillf Danton
2016-07-11 22:20 ` Andrew Morton
2016-07-12 6:32 ` Hillf Danton
2016-07-12 8:33 ` Mel Gorman [this message]
2016-07-12 8:48 ` Hillf Danton
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