Messages in this thread | | | Date | Wed, 18 Nov 2015 13:49:46 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/4] sched: introduce synchronized idle injection |
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On Wed, Nov 18, 2015 at 12:27:04PM +0000, Morten Rasmussen wrote: > On Wed, Nov 18, 2015 at 11:35:41AM +0100, Peter Zijlstra wrote: > > On Wed, Nov 18, 2015 at 09:36:22AM +0100, Ingo Molnar wrote: > > > What will such throttling do to latencies, as observed by user-space tasks? What's > > > the typical expected frequency of the throttling frequency that you are targeting? > > > > The default has 5ms (iirc) of forced idle, so depending on what you do, > > noticeable to outright painful. > > IIUC, it is 5 ticks, not ms.
The code uses hrtimers (badly), this means there _should_ not be a tick dependency.
> Which raises the question, doesn't that mean that we get disturbed four > times on each cpu during the forced idle period? So idle injection only > makes sense if the platform has package states with a target residency > less than a jiffy. Or, do we enter NOHZ idle? I haven't looked closely > enough to figure out yet.
The idea is to hit NOHZ.
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