Messages in this thread | | | Date | Thu, 18 May 2023 15:47:46 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH RESEND] sched/nohz: Add HRTICK_BW for using cfs bandwidth with nohz_full |
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On Thu, May 18, 2023 at 09:20:38AM -0400, Phil Auld wrote: > CFS bandwidth limits and NOHZ full don't play well together. Tasks > can easily run well past their quotas before a remote tick does > accounting. This leads to long, multi-period stalls before such > tasks can run again. Use the hrtick mechanism to set a sched > tick to fire at remaining_runtime in the future if we are on > a nohz full cpu, if the task has quota and if we are likely to > disable the tick (nr_running == 1). This allows for bandwidth > accounting before tasks go too far over quota. > > A number of container workloads use a dynamic number of real > nohz tasks but also have other work that is limited which ends > up running on the "spare" nohz cpus. This is an artifact of > having to specify nohz_full cpus at boot. Adding this hrtick > resolves the issue of long stalls on these tasks. > > Add the sched_feat HRTICK_BW off by default to allow users to > enable this only when needed.
OMG; so because NOHZ_FULL configuration sucks, we add hacks on?
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