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Date: Sat, 8 Dec 2007 16:41:22 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Michael Buesch <mb@bu3sch.de>
Cc: Mark Lord <lkml@rtr.ca>, Guillaume Chazarain <guichaz@yahoo.fr>,
       stefano.brivio@polimi.it, Nick Piggin <nickpiggin@yahoo.com.au>,
       Robert Love <rml@tech9.net>, linux-kernel@vger.kernel.org,
       Dave Jones <davej@redhat.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
       Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>, Len Brown <lenb@kernel.org>
Subject: Re: [PATCH] scheduler: fix x86 regression in native_sched_clock
Message-ID: <20071208154122.GE30270@elte.hu>
References: <20071207084559.GA11162@elte.hu> <200712081627.45937.mb@bu3sch.de> <20071208153327.GC30270@elte.hu> <200712081636.45828.mb@bu3sch.de>
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* Michael Buesch <mb@bu3sch.de> wrote:

> > i cannot see how. You can verify msleep by running something like this:
> > 
> >   while :; do time usleep 111000; done
> > 
> > you should see a steady stream of:
> > 
> >  real    0m0.113s
> >  real    0m0.113s
> >  real    0m0.113s
> > 
> > (on an idle system). If it fluctuates, with occasional longer delays, 
> > there's some timer problem present.
> 
> Does the sleeping and timing use different time references?

yes. But the real paranoid can do this from another box:

  while :; do time ssh testbox usleep 111000; done

	Ingo