From: Oleg Nesterov <oleg@tv-sign.ru>
To: Bj?rn Steinbrink <B.Steinbrink@gmx.de>
Cc: Petr Tesarik <ptesarik@suse.cz>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Roland McGrath <roland@redhat.com>,
Frank Mayhar <fmayhar@google.com>
Subject: Re: CPU POSIX timers livelock
Date: Fri, 2 May 2008 21:28:03 +0400 [thread overview]
Message-ID: <20080502172803.GA1541@tv-sign.ru> (raw)
In-Reply-To: <20080502164334.GA3585@atjola.homenet>
On 05/02, Bj?rn Steinbrink wrote:
>
> Hm, I have some message in that thread from April they don't seem to be
> on lkml.org nor in the bugzilla though. Oh well, I can send you an mbox
> of that thread in a private mail, just let me know if you want that.
Me too please ;)
Please note there is a related problem if we have a single thread but
a lot of timers attached to this thread. If the signal is ignored, each
timer should be re-armed, this all can consume >= 1/HZ CPU time.
We have "maxfire = 20" in check_thread_timers/check_process_timers to
prevent this, but it is just a workaround. And it is a bit silly to just
waste the CPU if the signal is ignored, arm_timer() is heavy and doesn't
scale well.
However, I have already forgot this code, perhaps I missed something,
and at least maxfire does help.
Oleg.
next prev parent reply other threads:[~2008-05-02 17:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-02 15:05 CPU POSIX timers livelock Petr Tesarik
2008-05-02 15:21 ` Björn Steinbrink
2008-05-02 16:13 ` Petr Tesarik
2008-05-02 16:43 ` Björn Steinbrink
2008-05-02 17:28 ` Oleg Nesterov [this message]
2008-05-02 17:10 ` Frank Mayhar
2008-05-17 0:16 ` CPU POSIX timers livelock (with patch for review) Frank Mayhar
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