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From: Ingo Molnar <mingo@elte.hu>
To: john stultz <johnstul@us.ibm.com>
Cc: John <me@privacy.net>,
	linux-kernel@vger.kernel.org, tglx@timesys.com, akpm@osdl.org,
	shill@free.fr
Subject: Re: One-shot high-resolution POSIX timer periodically late
Date: Wed, 24 Jan 2007 21:09:47 +0100	[thread overview]
Message-ID: <20070124200947.GA925@elte.hu> (raw)
In-Reply-To: <1169665347.6905.3.camel@localhost.localdomain>


* john stultz <johnstul@us.ibm.com> wrote:

> On Wed, 2007-01-24 at 10:41 +0100, John wrote:
> > I'm using the POSIX timers API. My platform is x86 running Linux
> > 2.6.18.6 patched with the high-resolution timer subsystem.
> > 
> > http://www.tglx.de/hrtimers.html

> > My process is the only SCHED_FIFO process on the system. There are 
> > no user-space processes with a higher priority. AFAICT, only a 
> > kernel thread could keep the CPU away from my app.
> > 
> > Is there a periodic kernel thread that runs every 2 seconds, cannot 
> > be preempted, and runs for over 50 µs??
> 
> This sounds like a BIOS SMI issue. Can you reproduce this behavior on 
> different hardware?

note that only the -hrt patchset is used - not the full -rt patchset - 
so 50 usecs delays (and more) are quite possible and common.

My question would be: does the same problem occur with the full -rt 
patchset and PREEMPT_RT? (see http://rt.wiki.kernel.org for details)

	Ingo

  reply	other threads:[~2007-01-24 20:11 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <45B729AF.4030701@privacy.net>
2007-01-24 19:02 ` john stultz
2007-01-24 20:09   ` Ingo Molnar [this message]
     [not found] <fa.NwnlFyMPfa3XG6my3HKGWnCW3x4@ifi.uio.no>
     [not found] ` <fa.Ji4GnAbBF2FR5JbSxvxn2haJZIk@ifi.uio.no>
2007-01-25  9:59   ` John
2007-01-25 22:19     ` john stultz
     [not found]   ` <fa.8TBiwbgs8B881k+3X+IlFjhqpLI@ifi.uio.no>
2007-01-25 12:03     ` John
     [not found] <fa.mtUvfgenNQkCc8835prYbwyiPQs@ifi.uio.no>
     [not found] ` <fa.lwkMc548uRMcUjd9KZ2pC1DMKT4@ifi.uio.no>
     [not found]   ` <fa.dTtI0ctv1nu+tCWiK6jGPnrX69k@ifi.uio.no>
     [not found]     ` <fa.CMU3scpnLxfHVWRFPcmfRl2CjhA@ifi.uio.no>
2007-01-30 17:38       ` John
2007-01-30 20:25         ` Ingo Molnar
     [not found] <fa.4zD54Ie6Ozt0P4YqQSicS+XzXGw@ifi.uio.no>
     [not found] ` <fa.G+/T32f2o1M3+YGLca/O8NaAQyY@ifi.uio.no>
     [not found]   ` <fa.6Ua8xjNfLKQEZZgDsoJgPMyww4g@ifi.uio.no>
     [not found]     ` <fa.yQlV+WU0TgrJTVqjopa01tgCnT0@ifi.uio.no>
     [not found]       ` <fa.ucVrLJ1Lh6FjdBHRglsIUc8/evk@ifi.uio.no>
     [not found]         ` <fa.Id9oufyELrVbe5Wb8SRakwC0V50@ifi.uio.no>
2007-02-01 10:18           ` John
2007-02-06 12:37             ` Ingo Molnar
2007-02-07 10:13               ` John
2007-02-05 16:37           ` John
2007-02-06  7:31             ` Peter Zijlstra
2007-02-07 10:25               ` John
2007-02-08 17:32                 ` Thomas Gleixner
2007-02-09 15:25                   ` John
2007-02-09 16:21                     ` Benedikt Spranger
2007-02-09 16:43                     ` Thomas Gleixner

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