From: Andrew Morton <akpm@osdl.org>
To: Dimitri Sivanich <sivanich@sgi.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Slab cache reap and CPU availability
Date: Fri, 21 May 2004 19:16:09 -0700 [thread overview]
Message-ID: <20040521191609.6f4a49a7.akpm@osdl.org> (raw)
In-Reply-To: <200405211541.i4LFfpar001544@fsgi142.americas.sgi.com>
Dimitri Sivanich <sivanich@sgi.com> wrote:
>
> Hi all,
>
> I have a fairly general question about the slab cache reap code.
>
> In running realtime noise tests on the 2.6 kernels (spinning to detect periods
> of CPU unavailability to RT threads) on an IA/64 Altix system, I have found the
> cache_reap code to be the source of a number of larger holdoffs (periods of
> CPU unavailability). These can last into the 100's of usec on 1300 MHz CPUs.
> Since this code runs periodically every few seconds as a timer softirq on all
> CPUs, holdoffs can occur frequently.
>
> Has anyone looked into less interruptive alternatives to running cache_reap
> this way (for the 2.6 kernel), or maybe looked into potential optimizations
> to the routine itself?
>
Do you have stack backtraces? I thought the problem was via the RCU
softirq callbacks, not via the timer interrupt. Dipankar spent some time
looking at the RCU-related problem but solutions are not comfortable.
What workload is triggering this?
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next prev parent reply other threads:[~2004-05-22 2:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-21 15:41 Dimitri Sivanich
2004-05-22 2:16 ` Andrew Morton [this message]
2004-05-24 15:39 ` Dimitri Sivanich
2004-05-24 21:53 ` Andrew Morton
2004-06-01 21:40 ` Dimitri Sivanich
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