Messages in this thread | | | Subject | Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM | From | Peter Zijlstra <> | Date | Wed, 08 Dec 2010 13:40:15 +0100 |
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On Sun, 2010-12-05 at 16:21 +0000, Russell King - ARM Linux wrote:
> I'm not sure that's the correct fix - it looks like sched_clock_cpu() > should already be preventing scheduler clock time going backwards. > > Hmm. IOP32x seems to have a 32-bit timer clocked at 200MHz. That means > it wraps once every 21s. However, we have that converted to ns by an > unknown multiplier and shift. It seems that those are chosen to > guarantee that we will cover only 4s without wrapping in the clocksource > conversion. Maybe that's not sufficient? > > Could you try looking into sched_clock_cpu(), sched_clock_local() and > sched_clock() to see whether anything odd stands out?
# git grep HAVE_UNSTABLE_SCHED_CLOCK arch/arm | wc -l 0
That code won't help if you don't enable it ;-)
John Stultz was also looking into making the kernel/sched_clock.c code deal with short clocks.
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