From: Vlastimil Babka <vbabka@suse.cz>
To: Simon Kirby <sim@hostway.ca>
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: Thu, 08 Jan 2015 13:10:45 +0100 [thread overview]
Message-ID: <54AE73C5.4000409@suse.cz> (raw)
In-Reply-To: <20150108010426.GB6664@hostway.ca>
On 01/08/2015 02:04 AM, Simon Kirby wrote:
> 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?
Yes, the code using this counter is either treating it as signed, or includes a
<0 tests. It's just the /proc output might be confusing here...
>> > 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-
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-01-08 12:16 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
2015-01-08 12:10 ` Vlastimil Babka [this message]
2015-01-07 9:44 ` Simon Kirby
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54AE73C5.4000409@suse.cz \
--to=vbabka@suse.cz \
--cc=holger.hoffstaette@googlemail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=sim@hostway.ca \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).