Messages in this thread | | | Subject | Re: [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg() | From | Steve Muckle <> | Date | Wed, 30 Mar 2016 18:42:20 -0700 |
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On 03/30/2016 12:35 PM, Peter Zijlstra wrote: > On Mon, Mar 28, 2016 at 12:38:26PM -0700, Steve Muckle wrote: >> Without covering all the paths where CFS utilization changes it's >> possible to have to wait up to a tick to act on some changes, since the >> tick is the only guaranteed regularly-occurring instance of the hook. >> That's an unacceptable amount of latency IMO... > > Note that even with your patches that might still be the case. Remote > wakeups might not happen on the destination CPU at all, so it might not > be until the next tick (which always happens locally) that we'll > 'observe' the utilization change brought with the wakeups. > > We could force all the remote wakeups to IPI the destination CPU, but > that comes at a significant performance cost.
What about only IPI'ing the destination when the utilization change is known to require a higher CPU frequency?
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