Messages in this thread | | | Subject | Re: [PATCH] x86: Reduce the default HZ value | From | Peter Zijlstra <> | Date | Thu, 07 May 2009 19:13:42 +0200 |
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On Thu, 2009-05-07 at 19:09 +0200, Peter Zijlstra wrote: > On Thu, 2009-05-07 at 10:13 -0400, Christoph Lameter wrote: > > I think we need to reduce the general tick frequency to be as low as > > possible. With high resolution timers the tick frequency is just the > > frequency with which the timer interrupt disturbs a running application. > > > > Are there any benefits remaining from frequent timer interrupts? I would > > think that 60 HZ would be sufficient. > > > > It would be good if the kernel would be truly tickless. Scheduler events > > would be driven by the scheduling intervals and not the invokations of the > > scheduler softirq. > > The only thing that's driven by the softirq is load-balancing, there's > way more to the scheduler-tick than kicking that thing awake every so > often. > > The problem is that running the scheduler of off hrtimers is too > expensive. We have the code, we tried it, people complained.
Therefore, decreasing the HZ value to say 50, we'd get a minimum involuntary preemption granularity of 20ms, something on the high end of barely usable.
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