Messages in this thread | | | Date | Wed, 22 Aug 2007 09:59:13 +0200 | From | Ingo Molnar <> | Subject | Re: [accounting regression since rc1] scheduler updates |
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* Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> Am Dienstag, 21. August 2007 schrieben Sie: > > could you try the patch below, does it work any better? > > I looked again at the scheduler code and things are getting better > when I run the patch below on top of your patch and with our > sched_clock prototype. I guess there is a reason why you want > rq->clock advanced by at least one tick?
yeah - on PCs if for whatever reason the TSC misbehaves (and that's quite frequent) then this code sets a minimum boundary for behavior. If sched_clock() is totally random or does not advance at all or goes backwards all the time then rq_clock() still functions and falls back to jiffies-granularity behavior in essence.
> We discussed calling scheduler_tick with virtual time as well. > Would it have the same result? > What would be the impact on latency?
if you call scheduler_tick() with virtual time then the "safety" measures in rq_clock() do not kick in and sched_clock() behaves correctly as far as the scheduler is concerned. (if everything is in virtual time then the scheduler has no way to observe/notice that in reality this is a virtual machine.)
> After looking at the current s390 timer code, it seems that this kind of > change is not trivial enough to be rc3+ ready. > I personally think, that for 2.6.23 we should use the patch against > fs/proc/array.c and everything else for 2.6.24?
yes, that has the least impact for .23 - i have added your array.c patch to my queue.
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