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From: Thomas Gleixner <tglx@linutronix.de>
To: Agustin Ferrin Pozuelo <agustin.ferrin@cgglobal.com>
Cc: "linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>
Subject: Re: 2.6.33.7-rt29 PREEMPT_RT worse latency than PREEMPT_DESKTOP on AT91?
Date: Wed, 15 Sep 2010 18:08:27 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1009151805540.2416@localhost6.localdomain6> (raw)
In-Reply-To: <4C90E959.80306@cgglobal.com>

On Wed, 15 Sep 2010, Agustin Ferrin Pozuelo wrote:
>  On 27/08/10 11:35, Thomas Gleixner wrote:
> > On Mon, 23 Aug 2010, Agustin Ferrin Pozuelo wrote:
> Sorry, my test setup is not very comprehensive at the moment. I have some
> overnight/overweekend results at hand with millions of loops:
> 
>     PREEMPT-DESKTOP:
>     root@at91sam9263cpc:~# time cyclictest -i 70000 -p 80 -h 700 -r

Oh, you are running cyclictest with a signal based timer and relative
time. Any reason for this ?

What happens if you change the command line to

   cyclictest -i 70000 -p 80 -n

> I am assuming context switching is more expensive on PREEMPT-RT under ARM9,
> where it seems already a bit expensive.

No, the context switch is equally expensive, but signal delivery might
be a bit more overhead on -RT

Thanks,

	tglx

  reply	other threads:[~2010-09-15 16:08 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-23 16:39 2.6.33.7-rt29 PREEMPT_RT worse latency than PREEMPT_DESKTOP on AT91? Agustin Ferrin Pozuelo
2010-08-27 10:35 ` Thomas Gleixner
2010-09-15 15:42   ` Agustin Ferrin Pozuelo
2010-09-15 16:08     ` Thomas Gleixner [this message]
2010-09-16 14:31       ` Agustin Ferrin Pozuelo

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