linux-kernel - Re: recomended way to check longest period that interupts are disabled ?

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Date:	Thu, 26 Apr 2007 19:15:23 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Mike Mattie <codermattie@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: recomended way to check longest period that interupts are
	disabled ?

On Thu, 2007-04-26 at 05:19 -0700, Mike Mattie wrote:
> Thanks for the comments. After running cyclictest it definitely looks
> like the average jitter is really low, around 7-8 . The max is really
> high , >100
> 
> If I am interpreting this correctly for the most part the jitter is
> pretty low, but something horrible is happening that blows up the
> max value.

Yup

> ./cyclictest -p 30 -t 6
> 2.00 1.84 1.41 3/120 13760
> 
> T: 0 (13130) P:30 I:1000 C:  42763 Min:      4 Act:   10 Avg:    8 Max:     133
> T: 1 (13131) P:29 I:1500 C:  28509 Min:      4 Act:    6 Avg:    7 Max:     114
> T: 2 (13132) P:28 I:2000 C:  21382 Min:      4 Act:    7 Avg:    6 Max:     157
> T: 3 (13133) P:27 I:2500 C:  17106 Min:      4 Act:   11 Avg:    7 Max:     110
> T: 4 (13134) P:26 I:3000 C:  14255 Min:      4 Act:    8 Avg:    7 Max:    1011
> T: 5 (13135) P:25 I:3500 C:  12218 Min:      4 Act:   12 Avg:    8 Max:     118

What happens with 

# cyclictest -p 80 -n

At first it puts the timer thread above everything else and second it
uses nanosleep instead of the signal delivered posix timers.

	tglx


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