On Fri, 2010-08-13 at 11:30 -0400, Adam Jackson wrote: > On Fri, 2010-08-13 at 13:08 +0800, ykzhao wrote: > > 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. > > On second thought, this seems like it's pretty awkward to use if we > don't know the granularity. And given that we're assuming milliseconds > everywhere, you'd need CONFIG_HZ >= 1000 to get that. Do we have a way > of getting HZ from userspace?
Naturally, right after I say this I find clock_getres(). - ajax
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