[alsa-devel] [PATCH] Modify mpc5200 AC97 driver to use V9 of spin_event_timeout()

Grant Likely grant.likely at secretlab.ca
Wed May 27 06:00:51 CEST 2009

On Tue, May 26, 2009 at 9:48 PM, Grant Likely <grant.likely at secretlab.ca> wrote:
> 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.  That being
> said, it needs to be balanced with the context switch overhead.  If
> 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.


Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

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