Messages in this thread | | | Date | Thu, 26 Jun 2014 16:38:11 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH v2 1/3] sched/fair: Disable runtime_enabled on dying rq |
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* Kirill Tkhai <ktkhai@parallels.com> [2014-06-24 11:53:52]:
> We kill rq->rd on the CPU_DOWN_PREPARE stage: > > cpuset_cpu_inactive -> cpuset_update_active_cpus -> partition_sched_domains -> > -> cpu_attach_domain -> rq_attach_root -> set_rq_offline > > This unthrottles all throttled cfs_rqs. > > But the cpu is still able to call schedule() till > > take_cpu_down->__cpu_disable() > > is called from stop_machine. > > This case the tasks from just unthrottled cfs_rqs are pickable > in a standard scheduler way, and they are picked by dying cpu. > The cfs_rqs becomes throttled again, and migrate_tasks() > in migration_call skips their tasks (one more unthrottle > in migrate_tasks()->CPU_DYING does not happen, because rq->rd > is already NULL). > > Patch sets runtime_enabled to zero. This guarantees, the runtime > is not accounted, and the cfs_rqs won't exceed given > cfs_rq->runtime_remaining = 1, and tasks will be pickable > in migrate_tasks(). runtime_enabled is recalculated again > when rq becomes online again. > > Ben Segall also noticed, we always enable runtime in > tg_set_cfs_bandwidth(). Actually, we should do that for online > cpus only. To fix that, we check if a cpu is online when > its rq is locked. This guarantees we do not have races with > set_rq_offline(), which also requires rq->lock. > > v2: Fix race with tg_set_cfs_bandwidth(). > Move cfs_rq->runtime_enabled=0 above unthrottle_cfs_rq(). > > Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> > CC: Konstantin Khorenko <khorenko@parallels.com> > CC: Ben Segall <bsegall@google.com> > CC: Paul Turner <pjt@google.com> > CC: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > CC: Mike Galbraith <umgwanakikbuti@gmail.com> > CC: Peter Zijlstra <peterz@infradead.org> > CC: Ingo Molnar <mingo@kernel.org>
looks good to me.
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
-- Thanks and Regards Srikar Dronamraju
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