From: Grant Edwards <grant.b.edwards@gmail.com>
To: linux-rt-users@vger.kernel.org
Subject: Re: Using patch-2.6.33.7.2-rt30 increases latency and CPU usage?
Date: Wed, 9 May 2012 22:00:00 +0000 (UTC) [thread overview]
Message-ID: <joepd0$e4f$1@dough.gmane.org> (raw)
In-Reply-To: joemui$6v0$1@dough.gmane.org
On 2012-05-09, Grant Edwards <grant.b.edwards@gmail.com> wrote:
> IOW: the real-time patch for 2.6.33.7 makes both the typical interrupt
> latency and the CPU usage significantly worse.
>
> Typical latency without the RT patch is 5-15us.
>
> Typical latency with is 15-50us (I've never seen latency below 15us
> with the RT patch).
>
> Is this the expected behavior?
I've been loaned a clue by somebody on the OSADL mailing list: the RT
patches are for improving _user_space_ reponse, and may do so at the
expense of both CPU usage and interrupt latency.
As a result, I'm better off without the RT patch if what I care about
is interrupt latency.
Am right I correct in the following conclusions?
* In 2.6.33.7, ISRs are really ISRs
* In 2.6.33.7-rt30, ISRs are kernel threads.
--
Grant Edwards grant.b.edwards Yow! Don't hit me!! I'm in
at the Twilight Zone!!!
gmail.com
next prev parent reply other threads:[~2012-05-09 22:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-09 21:18 Using patch-2.6.33.7.2-rt30 increases latency and CPU usage? Grant Edwards
2012-05-09 22:00 ` Grant Edwards [this message]
2012-05-09 22:13 ` Joachim Achtzehnter
2012-05-09 23:18 ` Grant Edwards
2012-05-10 9:46 ` Remy Bohmer
2012-05-10 13:53 ` Grant Edwards
2012-05-11 13:42 ` Remy Bohmer
2012-05-11 13:56 ` Grant Edwards
2012-05-11 18:46 ` Tim Sander
2012-05-15 17:33 ` Steven Rostedt
2012-05-15 22:58 ` Grant Edwards
2012-05-15 23:06 ` Steven Rostedt
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