From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Daniel J Blueman <daniel@numascale-asia.com>
Cc: "Paul E. McKenney" <paul.mckenney@linaro.org>,
Steffen Persvold <sp@numascale.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: False-positive RCU stall warnings on large systems...
Date: Tue, 19 Feb 2013 10:16:24 -0800 [thread overview]
Message-ID: <20130219181624.GG3093@linux.vnet.ibm.com> (raw)
In-Reply-To: <5123A984.4000704@numascale-asia.com>
On Wed, Feb 20, 2013 at 12:34:12AM +0800, Daniel J Blueman wrote:
> Hi Paul,
>
> On some of our larger servers with many hundreds of cores and when
> under high duress, we can see scheduler RCU stall warnings [1], so
> find we have to increase the hardcoded RCU_STALL_RAT_DELAY up from 2
> and RCU_JIFFIES_TILL_FORCE_QS up from 3.
>
> Is there a more sustainable way to account for this to avoid it
> being hard-coded, such as making it and dependent timeouts a
> fraction of CONFIG_RCU_CPU_STALL_TIMEOUT?
>
> On the other hand, perhaps this is just caused by clock jitter (eg
> due to distance from a contended clock source)? So increasing these
> a bit may just be adequate in general...
Hmmm... What version of the kernel are you running?
Thanx, Paul
> Many thanks,
> Daniel
>
> --- [1]
>
> [ 3939.010085] INFO: rcu_sched detected stalls on CPUs/tasks: {}
> (detected by 1, t=29662 jiffies, g=3053, c=3052, q=598)
> [ 3939.020008] INFO: Stall ended before state dump start
> --
> Daniel J Blueman
> Principal Software Engineer, Numascale Asia
>
next prev parent reply other threads:[~2013-02-19 18:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-19 16:34 False-positive RCU stall warnings on large systems Daniel J Blueman
2013-02-19 18:16 ` Paul E. McKenney [this message]
2013-02-20 3:35 ` Daniel J Blueman
2013-02-25 16:32 ` Paul E. McKenney
2013-03-05 9:02 ` Daniel J Blueman
2013-03-06 17:03 ` Paul E. McKenney
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