Messages in this thread | | | Date | Mon, 22 Aug 2016 12:19:49 +0000 | From | Nicholas Mc Guire <> | Subject | Re: [PATCH RFC] rcuperf: make timeout HZ independent |
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On Mon, Aug 22, 2016 at 04:49:43AM -0700, Paul E. McKenney wrote: > On Mon, Aug 22, 2016 at 01:21:05PM +0200, Nicholas Mc Guire wrote: > > Make the probability of ftrace dump not interfering with other writers > > grace period, HZ independent. > > > > Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org> > > What we would -really- like is to vary the time based on the clock rate > of the CPUs (could use bogomips, I suppose) and the memory latency of > the system, so that systems with smaller memory latency and faster CPUs > would use shorter timeouts. However, slower CPUs tend to use smaller > HZ values, so varying based on HZ is not entirely insane. > > But what would you suggest?
so what you want is a rough estimate of a "fixed instruction quantum" while bogomips/cpu_khz would ignore memory latency it might still be better than a fixed time then - something like schedule_timeout(msecs_to_jiffies(10000/cpu_khz)); ?
> > Good question on schedule_timeout_interruptible()... I usually do that > if there is some reason to be sensitive to an early wakeup, for example, > to allow shutdown to proceed quickly, but that doesn't make much sense > here, given that ftrace_dump() is likely to take a very long time. > ok - just though that I was overlooking something - thanks for the clarification.
thx! hofrat
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