From: Ingo Molnar <mingo@elte.hu>
To: Mark_H_Johnson@raytheon.com
Cc: Amit Shah <amit.shah@codito.com>,
Karsten Wiese <annabellesgarden@yahoo.de>,
Bill Huey <bhuey@lnxw.com>, Adam Heath <doogie@debian.org>,
emann@mrv.com, Gunther Persoons <gunther_persoons@spymac.com>,
"K.R. Foley" <kr@cybsft.com>,
linux-kernel@vger.kernel.org,
Florian Schmidt <mista.tapas@gmx.net>,
Fernando Pablo Lopez-Lezcano <nando@ccrma.Stanford.EDU>,
Lee Revell <rlrevell@joe-job.com>,
Rui Nuno Capela <rncbc@rncbc.org>,
Shane Shrybman <shrybman@aei.ca>,
Esben Nielsen <simlo@phys.au.dk>,
Thomas Gleixner <tglx@linutronix.de>,
Michal Schmidt <xschmi00@stud.feec.vutbr.cz>
Subject: Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15
Date: Fri, 10 Dec 2004 22:24:51 +0100 [thread overview]
Message-ID: <20041210212451.GF5864@elte.hu> (raw)
In-Reply-To: <OF8AB2B6D9.572374AA-ON86256F66.0061EFA8-86256F66.0061F00A@raytheon.com>
* Mark_H_Johnson@raytheon.com <Mark_H_Johnson@raytheon.com> wrote:
> [...] I also had several cases where I "triggered" a trace but no
> output - I assume those are related symptoms. For example:
>
> # ./cpu_delay 0.000100
> Delay limit set to 0.00010000 seconds
> calibrating loop ....
> time diff= 0.504598 or 396354830 loops/sec.
> Trace activated with 0.000100 second delay.
> Trace triggered with 0.000102 second delay. [not recorded]
> Trace activated with 0.000100 second delay.
> Trace triggered with 0.000164 second delay. [not recorded]
is the userspace delay measurement nested inside the kernel-based
method? I.e. is it something like:
gettimeofday(0,1);
timestamp1 = cycles();
... loop some ...
timestamp2 = cycles();
gettimeofday(0,0);
and do you get 'unreported' latencies in such a case too? If yes then
that would indeed indicate a tracer bug. But if the measurement is done
like this:
gettimeofday(0,1);
timestamp1 = cycles();
... loop some ...
gettimeofday(0,0); // [1]
timestamp2 = cycles(); // [2]
then a delay could get inbetween [1] and [2].
OTOH if the 'loop some' time is long enough then the [1]-[2] window is
too small to be significant statistically, while your logs show a near
50% 'miss rate'.
Ingo
next prev parent reply other threads:[~2004-12-10 21:25 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-10 17:49 [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15 Mark_H_Johnson
2004-12-10 21:09 ` Ingo Molnar
2004-12-10 21:12 ` Ingo Molnar
2004-12-10 21:24 ` Ingo Molnar [this message]
2004-12-13 0:16 ` Fernando Lopez-Lezcano
2004-12-13 6:47 ` Ingo Molnar
2004-12-14 0:46 ` Fernando Lopez-Lezcano
2004-12-14 4:42 ` K.R. Foley
2004-12-14 8:47 ` Rui Nuno Capela
2004-12-14 11:35 ` Ingo Molnar
2004-12-27 14:35 ` Real-time rw-locks (Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15) Esben Nielsen
2004-12-27 15:27 ` Steven Rostedt
2004-12-27 16:23 ` Esben Nielsen
2004-12-27 16:39 ` Steven Rostedt
2004-12-27 21:06 ` Bill Huey
2004-12-27 21:48 ` Valdis.Kletnieks
2004-12-28 21:59 ` Lee Revell
2005-01-04 15:25 ` Andrew McGregor
2004-12-28 21:42 ` Lee Revell
2005-01-28 7:38 ` Ingo Molnar
2005-01-28 11:56 ` William Lee Irwin III
2005-01-28 15:28 ` Ingo Molnar
2005-01-28 15:55 ` William Lee Irwin III
2005-01-28 16:16 ` Ingo Molnar
2005-01-28 19:18 ` Trond Myklebust
2005-01-28 19:45 ` Ingo Molnar
2005-01-28 23:25 ` Bill Huey
2005-01-28 21:13 ` Lee Revell
2005-01-30 22:03 ` Esben Nielsen
2005-01-30 23:59 ` Kyle Moffett
-- strict thread matches above, loose matches on Subject: below --
2004-12-13 23:14 [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15 Mark_H_Johnson
2004-12-13 20:02 Mark_H_Johnson
2004-12-13 22:39 ` Ingo Molnar
2004-12-13 17:05 Mark_H_Johnson
2004-12-13 22:33 ` Ingo Molnar
2004-12-10 22:06 Mark_H_Johnson
2004-12-10 22:24 ` Ingo Molnar
2004-12-10 21:58 Mark_H_Johnson
2004-12-10 21:54 Mark_H_Johnson
2004-12-10 22:14 ` Ingo Molnar
2004-12-10 21:31 Mark_H_Johnson
2004-12-10 21:54 ` Ingo Molnar
2004-12-10 21:06 Mark_H_Johnson
2004-12-10 21:40 ` Ingo Molnar
2004-12-10 20:03 Mark_H_Johnson
2004-12-09 21:58 [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-6 Mark_H_Johnson
2004-12-09 22:55 ` Ingo Molnar
2004-12-10 10:53 ` [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15 Ingo Molnar
2004-12-10 14:59 ` Gene Heskett
2004-12-10 15:59 ` Gene Heskett
2004-12-10 19:09 ` Lee Revell
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