From: Simon Kirby <sim@hostway.ca>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Holger Hoffst?tte <holger.hoffstaette@googlemail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: Dirty pages underflow on 3.14.23
Date: Wed, 7 Jan 2015 17:04:26 -0800 [thread overview]
Message-ID: <20150108010426.GB6664@hostway.ca> (raw)
In-Reply-To: <54ADA99A.90501@suse.cz>
On Wed, Jan 07, 2015 at 10:48:10PM +0100, Vlastimil Babka wrote:
> On 01/07/2015 10:28 PM, Simon Kirby wrote:
>
> > Hmm...A possibly-related issue...Before trying this, after a fresh boot,
> > /proc/vmstat showed:
> >
> > nr_alloc_batch 4294541205
>
> This can happen, and not be a problem in general. However, there was a fix
> abe5f972912d086c080be4bde67750630b6fb38b in 3.17 for a potential performance
> issue if this counter overflows on single processor configuration. It was marked
> stable, but the 3.16 series was discontinued before the fix could be backported.
> So if you are on single-core, you might hit the performance issue.
That particular commit seems to just change the code path in that case,
but should it be underflowing at all on UP?
> > Still, nr_alloc_batch reads as 4294254379 after MySQL restart, and now
> > seems to stay up there.
>
> Hm if it stays there, then you are probably hitting the performance issue. Look
> at /proc/zoneinfo, which zone has the underflow. It means this zone will get
> unfair amount of allocations, while others may contain stale data and would be
> better candidates.
In this case, it has only 640MB, and there's only DMA and Normal. This is
affecting Normal, and DMA is so small that it probably doesn't matter.
Simon-
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next prev parent reply other threads:[~2015-01-08 1:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-05 23:05 Dirty pages underflow on 3.14.23 Mikulas Patocka
2015-01-06 15:02 ` Johannes Weiner
2015-01-06 17:54 ` Mikulas Patocka
2015-01-07 10:57 ` Holger Hoffstätte
2015-01-07 21:28 ` Simon Kirby
2015-01-07 21:48 ` Vlastimil Babka
2015-01-08 1:04 ` Simon Kirby [this message]
2015-01-08 12:10 ` Vlastimil Babka
2015-01-07 9:44 ` Simon Kirby
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