From: Arjan van de Ven <arjan@infradead.org>
To: Shawn Bohrer <shawn.bohrer@gmail.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: High scheduler wake up times
Date: Sun, 31 Jan 2010 10:28:46 -0800 [thread overview]
Message-ID: <20100131102846.4d1e18aa@infradead.org> (raw)
In-Reply-To: <20100131034718.GE27390@mediacenter.gateway.2wire.net>
On Sat, 30 Jan 2010 21:47:18 -0600
Shawn Bohrer <shawn.bohrer@gmail.com> wrote:
>
> Of course that patch makes my situation worse, which was my point. We
> are depending on the _current_ epoll_wait() implementation which calls
> schedule_timeout(1).
> You do agree that the current epoll_wait()
> implementation sleeps less than 1 msec with HZ == 1000 correct?
I agree with your hypothesis, but I wouldn't call the behavior
correct ;-)
First of all, jiffies based timeouts are supposed to round *up*, not
down, and second.. it should really be just 1 msec.
> With the old kernel I can run 500 of these processes, and I'm hoping
> that I'm simply missing the knob I need to tweak to achieve similar
> performance on a recent kernel.
can you run powertop during your workload? maybe you're getting hit by
some C state exit latencies tilting the rounding over the top just too
many times...
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2010-01-31 18:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-30 23:45 High scheduler wake up times Shawn Bohrer
2010-01-30 23:56 ` Arjan van de Ven
2010-01-31 0:29 ` Shawn Bohrer
2010-01-31 0:02 ` Arjan van de Ven
2010-01-31 0:11 ` Arjan van de Ven
2010-01-31 0:35 ` Shawn Bohrer
2010-01-31 0:46 ` Shawn Bohrer
2010-01-31 0:47 ` Arjan van de Ven
2010-01-31 3:47 ` Shawn Bohrer
2010-01-31 18:28 ` Arjan van de Ven [this message]
2010-01-31 20:50 ` Shawn Bohrer
2010-02-01 8:51 ` Peter Zijlstra
2010-02-01 19:37 ` Shawn Bohrer
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