linux-kernel - Re: Reading /proc/slabinfo causes stalls

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Message-ID: <CAMjP1KmGS1D6KU5hmugyPB+YZ-RhfBxjxHgMM2g3UuCvU6FgyQ@mail.gmail.com>
Date:	Tue, 16 Oct 2012 13:25:16 -0500
From:	Avleen Vig <avleen@...il.com>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Reading /proc/slabinfo causes stalls

By default we use the 2.6.32-279.5.2 as provided by CentOS.
However I also tried the 3.0.46 from elrepo:
http://elrepo.org/linux/kernel/el6/x86_64/RPMS/

The config for the 3.0 kernel is:
https://gist.github.com/3901068

They both seem to exhibit the same problem.

Thanks :)

On Tue, Oct 16, 2012 at 1:04 PM, Pekka Enberg <penberg@...nel.org> wrote:
> Hi Avleen,
>
> On Tue, Oct 16, 2012 at 8:51 PM, Avleen Vig <avleen@...il.com> wrote:
>> I *think* this is the right place to ask this, and apologies if it's not
>> (is there a better place?).
>>
>> We have checks which read /proc/slabinfo once a minute, and have noticed
>> that this causes the entire system to stall for a few milliseconds.
>> It's long enough that it causes noticeable delays in latency-sensitive
>> applications (between 10ms and 100ms).
>>
>> Is this a known condition? Are there work arounds or other ways to get the
>> slab allocation data which don't cause stalls?
>
> What kernel version are you using? What does your .config look like?
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