Messages in this thread | | | Subject | Re: [patch] prefer TSC over PM Timer | From | Alan Cox <> | Date | Wed, 17 Nov 2004 15:25:01 +0000 |
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On Maw, 2004-11-16 at 00:23, dean gaudet wrote: > i've heard other folks have independently run into this problem -- in fact > i see the most recent fc2 kernels already do this. i'd like this to be > accepted into the main kernel though.
IMHO it was a mistake to make this change in FC2.
> the x86 PM Timer is an order of magnitude slower than the TSC for > gettimeofday calls. i'm seeing 8%+ of the time spent doing gettimeofday > in someworkloads... and apparently kernel.org was seeing 80% of its time > go to gettimeofday during the fc3-release overload. PM timer is also less > accurate than TSC.
Nobody guarantees that the TSC is clocked at the same rate per CPU and several power management schemes break it. I see it break on my Thinkpad 600 and its one reason I have to replace the FC kernel with a 2.6-ac kernel on that system.
Is gettimeofday supposed to return the right value or be fast ?
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