From: Grant Likely <grant.likely@secretlab.ca>
To: Jon Smirl <jonsmirl@gmail.com>
Cc: linuxppc-dev@ozlabs.org, alsa-devel@alsa-project.org,
Timur Tabi <timur@freescale.com>,
broonie@sirena.org.uk
Subject: Re: [alsa-devel] [PATCH] Modify mpc5200 AC97 driver to use V9 of spin_event_timeout()
Date: Tue, 26 May 2009 22:00:51 -0600 [thread overview]
Message-ID: <fa686aa40905262100v64a01d41q65ff39ad953305a3@mail.gmail.com> (raw)
In-Reply-To: <fa686aa40905262048ma2d5e12s907c489974343280@mail.gmail.com>
On Tue, May 26, 2009 at 9:48 PM, Grant Likely <grant.likely@secretlab.ca> w=
rote:
> First, udelay just burns time, and if the delay is too large, then the
> it is wasting time that could be used for something else. =A0That being
> said, it needs to be balanced with the context switch overhead. =A0If
> the udelay() is less than double the context switch time, then the
> overhead is greater than the time spent spinning.
BTW, lmbench lat_ctx test case tells me that context switch latency is
measured somewhere around 30 to 60 us for user space processes
sleeping on a file descriptor. That will be lower for kernel threads
since there is no syscall overhead to account for.
g.
--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
prev parent reply other threads:[~2009-05-27 4:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-27 0:25 [PATCH] Modify mpc5200 AC97 driver to use V9 of spin_event_timeout() Jon Smirl
2009-05-27 0:38 ` [alsa-devel] " Timur Tabi
2009-05-27 0:44 ` Jon Smirl
2009-05-27 0:53 ` Timur Tabi
2009-05-27 1:01 ` Jon Smirl
2009-05-27 3:12 ` Timur Tabi
2009-05-27 3:49 ` Grant Likely
2009-05-27 3:48 ` Grant Likely
2009-05-27 4:00 ` Grant Likely [this message]
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