[RFC] use CLOCK_MONOTONIC_COARSE posix timer instead of CLOCK_MONOTONIC when calling the function of clock_gettime in xserver/os/util.c

[ykzhao]

On Fri, 2010-08-13 at 11:32 +0800, Julien Cristau wrote:
> On Thu, Aug 12, 2010 at 09:47:23 +0800, ykzhao wrote:
> 
> > when playing flash h.264 cif video workload, the cpu C0 usage is reduced
> > from 43% to 42% while the video quality is not affected.
> > 
> Is 43% vs 42% a really significant win?  How close is it to measurement
> noise?

The purpose of using CLOCK_MONOTONIC_COARSE posix timer is to reduce
the overhead of read_hpet. 

Yes. The 1% ratio seems tiny. But the tiny ratio is related with that
the total overhead of read_hpet is not very high on the CPU usage(about
3%) when playing the video workload. In such case it is not easy to get
one higher improvement.


> 
> Cheers,
> Julien