From: Chris Worley <chris.worley@primarydata.com>
To: Jeff Layton <jlayton@poochiereds.net>
Cc: Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org, bfields@fieldses.org,
Michael Skralivetsky <michael.skralivetsky@primarydata.com>,
Trond Myklebust <trond.myklebust@primarydata.com>,
Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: Re: timer code oops when calling mod_delayed_work
Date: Mon, 2 Nov 2015 09:48:41 -1000 [thread overview]
Message-ID: <CABz_YQ7fKYYL7jbp+XfFLHG61ZhxPUA8cAq92Vn2vkKzEtAR3Q@mail.gmail.com> (raw)
In-Reply-To: <20151031175404.3c57a17a@tlielax.poochiereds.net>
On Sat, Oct 31, 2015 at 11:54 AM, Jeff Layton <jlayton@poochiereds.net> wrote:
> On Sat, 31 Oct 2015 17:31:07 -0400
> Tejun Heo <tj@kernel.org> wrote:
...
>>
>> > I have asked Chris and Michael to see if they can bisect it down, but
>> > it may be a bit before they can get that done. Any insight you might
>> > have in the meantime would helpful.
>>
>> Yeah, I'd love to find out how reproducible the issue is. If the
>> problem is rarely reproducible, it might make sense to try
>> instrumentation before trying bisection as it *could* be a latent bug
>> which has been there all along and bisecting to the commit introducing
>> the code wouldn't help us too much.
>>
>
> It seems fairly reproducible, at least on v4.3-rc7 kernels:
>
> This came about when I asked them to perf test some nfsd patches that I
> have queued up. I patched a Fedora 4.3-rc7 kernel and wanted to see
> what the perf delta was (with NFSv3, fwiw):
>
> Patched kernels here: http://koji.fedoraproject.org/koji/taskinfo?taskID=11598089
>
> Unpatched kernels here: http://koji.fedoraproject.org/koji/buildinfo?buildID=694377
>
> Michael was using the SPEC SFS VDI workload to test, and was able to
> get the same panic on both kernels. So it does seem to be reproducible.
> It might even be possible to tune the VM to make the shrinker fire more
> often, which may help tickle this more.
>
> In any case, I've asked them to try something v4.2-ish and see if it's
> reproducible there, and then try v4.1 if it is. I figure anything
> earlier is probably not worth testing if it still fails on v4.1. If it
> turns out not to be reproducible on those earlier kernels then we can
> bisect from there to track it down.
The trick seems to be the NFS thread count: I initially though this
was SFS/VDI specific, but when I ratcheted up the thread count to what
Michael was using, 256 threads oopses on fio (throughput) benchmarks
too.
In bisecting kernels, it appeared between 4.2.3-200 and 4.2.5-200 (all
the 4.2.4 kernels were bad).
Jeff has a lead on this...
Chris
next prev parent reply other threads:[~2015-11-02 19:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-29 14:31 timer code oops when calling mod_delayed_work Jeff Layton
2015-10-29 17:58 ` Jeff Layton
2015-10-31 2:00 ` Tejun Heo
2015-10-31 11:34 ` Jeff Layton
2015-10-31 21:31 ` Tejun Heo
2015-10-31 21:54 ` Jeff Layton
2015-11-02 19:48 ` Chris Worley [this message]
2015-11-02 19:56 ` Jeff Layton
2015-11-03 1:33 ` Jeff Layton
2015-11-03 17:55 ` Jeff Layton
2015-11-03 22:54 ` Tejun Heo
2015-11-04 0:06 ` Tejun Heo
2015-11-04 11:48 ` Jeff Layton
2015-11-04 17:15 ` [PATCH] timer: add_timer_on() should perform proper migration Tejun Heo
2015-11-04 19:27 ` [tip:timers/urgent] timers: Use proper base migration in add_timer_on() tip-bot for Tejun Heo
2015-11-04 19:35 ` [PATCH] timer: add_timer_on() should perform proper migration Thomas Gleixner
2015-11-04 19:43 ` Tejun Heo
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