Messages in this thread | | | Date | Wed, 18 Nov 2015 14:04:41 +0000 | From | Morten Rasmussen <> | Subject | Re: [PATCH 3/4] sched: introduce synchronized idle injection |
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On Wed, Nov 18, 2015 at 01:49:46PM +0100, Peter Zijlstra wrote: > 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.
Then I'm confused :-/
I see the hrtimers, but the actual idle duration appears to be in ticks rather than ms and then converted later.
+/* Duration of idle time in ticks of each injection period */ +unsigned int sysctl_sched_cfs_idle_inject_duration = 5UL;
...and futher down we have:
+ duration_msec = jiffies_to_msecs(sysctl_sched_cfs_idle_inject_duration);
I will go back and look harder.
> > > 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.
Nice!
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