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From: Pradyumna Sampath <pradysam@gmail.com>
To: "M. Koehrer" <mathias_koehrer@arcor.de>
Cc: linux-rt-users@vger.kernel.org, rachana.rao@in.abb.com
Subject: Re: mq_timedrecieve timeout accuracy
Date: Wed, 24 Mar 2010 15:03:50 +0100	[thread overview]
Message-ID: <6d09081c1003240703o19ad3dffx20abae9d15e2d0b@mail.gmail.com> (raw)
In-Reply-To: <6d09081c1003240637w28ee6861tfcef4c7876ef3e40@mail.gmail.com>

Hi,

On Wed, Mar 24, 2010 at 2:37 PM, Pradyumna Sampath <pradysam@gmail.com> wrote:
> John, mq_timedrecieve takes abstime. Isnt it supposed to be
> CLOCK_REALTIME ? Anyway, I tried with MONOTONIC .. mq_timedrecieve
> doesnt block on that.
>
> I was just looking at some code in the kernel. linux/ipc/mqueue.c
> +442. This line says:
>
> time = schedule_timeout(timeout);
>
> Maybe this is why produces a timeout that is inaccurate. Shouldnt it
> be schedule_hrtimeout ?

Ok, I just moved the HZ value from 250 to 1000 and the accuracy has
improved significantly from 5-7 to 1-2 miliseconds. But IMHO, we
should still change schedule_timeout to schedule_hrtimeout for better
accuracy on the timeout because in many cases 1-2 miliseconds is just
not good enough.

I will try to push out a patch for this later today.

regards
/prady

-- 
http://www.prady.in

  parent reply	other threads:[~2010-03-24 14:03 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-24 12:27 mq_timedrecieve timeout accuracy Pradyumna Sampath
2010-03-24 13:12 ` John Kacur
2010-03-24 13:21 ` Sujit K M
2010-03-24 13:22 ` M. Koehrer
2010-03-24 13:37   ` Pradyumna Sampath
2010-03-24 13:45     ` Sujit K M
2010-03-24 13:47       ` Pradyumna Sampath
2010-03-24 14:03     ` Pradyumna Sampath [this message]
2010-03-24 15:46       ` [PATCH] " Pradyumna Sampath
2010-03-29 15:08         ` [PATCH] " Carsten Emde
2010-03-30  7:41           ` Pradyumna Sampath

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