Messages in this thread | | | Date | Mon, 26 Aug 2019 11:25:06 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] sched/fair: don't assign runtime for throttled cfs_rq |
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On Sat, Aug 24, 2019 at 05:15:58PM +0800, Liangyan wrote: > do_sched_cfs_period_timer() will refill cfs_b runtime and call > distribute_cfs_runtime() to unthrottle cfs_rq, sometimes cfs_b->runtime > will allocate all quota to one cfs_rq incorrectly. > This will cause other cfs_rq can't get runtime and will be throttled. > We find that one throttled cfs_rq has non-negative > cfs_rq->runtime_remaining and cause an unexpetced cast from s64 to u64 > in snippet: distribute_cfs_runtime() { > runtime = -cfs_rq->runtime_remaining + 1; }. > This cast will cause that runtime will be a large number and > cfs_b->runtime will be subtracted to be zero at last. > According to Ben Segall, the throttled cfs_rq can have > account_cfs_rq_runtime called on it because it is throttled before > idle_balance, and the idle_balance calls update_rq_clock to add time > that is accounted to the task.
That is distinctly unreadable. Please try again with a little bit of whitespace added.
> This commit prevents cfs_rq to be assgined new runtime if it has been > throttled to avoid the above incorrect type cast. > > Signed-off-by: Liangyan <liangyan.peng@linux.alibaba.com> > Reviewed-by: Ben Segall <bsegall@google.com> > Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
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