Date: Fri, 18 Nov 2005 18:57:59 -0500 (EST)
From: Steven Rostedt <rostedt@goodmis.org>
To: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
cc: Lee Revell <rlrevell@joe-job.com>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, "Paul E. McKenney" <paulmck@us.ibm.com>,
       "K.R. Foley" <kr@cybsft.com>, Thomas Gleixner <tglx@linutronix.de>,
       pluto@agmk.net, john cooper <john.cooper@timesys.com>,
       Benedikt Spranger <bene@linutronix.de>,
       Daniel Walker <dwalker@mvista.com>,
       Tom Rini <trini@kernel.crashing.org>,
       George Anzinger <george@mvista.com>
Subject: Re: 2.6.14-rt13
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On Fri, 18 Nov 2005, Fernando Lopez-Lezcano wrote:

> > Can it simply be pinned to a cpu?
>
> Is there a way to know in which cpu a process is running? At least Jack
> could ignore timinig issues if the measurement is going to happen in a
> different cpu than the one where the original timestamp was collected.
>

Simple answer? No. At least not meaningfully.

If you do:

cpu = fictitious_get_my_cpu();
if (cpu == last_cpu()) {
	rdtsc(oldtime);
	...
}

There's no guarantee that jack doesn't switch cpu's from when it found out
what CPU it was on to doing the calculation.  So it would be easier to pin
it.

(apt-get schedutils)

man 1 taskset

or if you modify the code:

mn 2 sched_setaffinity

-- Steve


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