Messages in this thread | | | From | Pavan Kondeti <> | Date | Thu, 3 Nov 2016 21:03:45 +0530 | Subject | Re: [PATCH 1/4] sched: move IO scheduling accounting from io_schedule_timeout() to __schedule() |
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Hi Tejun,
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 94732d1..f6baa38 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3336,11 +3336,17 @@ static void __sched notrace __schedule(bool preempt) > unsigned long *switch_count; > struct pin_cookie cookie; > struct rq *rq; > - int cpu; > + int cpu, in_iowait; > > cpu = smp_processor_id(); > rq = cpu_rq(cpu); > prev = rq->curr; > + in_iowait = prev->in_iowait; > + > + if (in_iowait) { > + delayacct_blkio_start(); > + atomic_inc(&rq->nr_iowait); > + } > > schedule_debug(prev); > > @@ -3406,6 +3412,11 @@ static void __sched notrace __schedule(bool preempt) > } > > balance_callback(rq); > + > + if (in_iowait) { > + atomic_dec(&rq->nr_iowait); > + delayacct_blkio_end(); > + } > }
I think, the nr_iowait update can go wrong here.
When the task migrates to a different CPU upon wakeup, this rq points to a different CPU from the one on which nr_iowait is incremented before.
Thanks, Pavan
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