Messages in this thread | | | From | bsegall@google ... | Subject | Re: [PATCH v2 2/2] sched/fair: Advance global expiration when period timer is restarted | Date | Wed, 20 Jun 2018 10:02:01 -0700 |
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Xunlei Pang <xlpang@linux.alibaba.com> writes:
> When period gets restarted after some idle time, start_cfs_bandwidth() > doesn't update the expiration information, expire_cfs_rq_runtime() will > see cfs_rq->runtime_expires smaller than rq clock and go to the clock > drift logic, wasting needless cpu cycles on the scheduler hot path. > > Update the global expiration in start_cfs_bandwidth() to avoid frequent > expire_cfs_rq_runtime() calls once a new period begins. > > Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com> Reviewed-By: Ben Segall <bsegall@google.com>
> --- > kernel/sched/fair.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index e6bb68d52962..f167aca066cc 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5204,13 +5204,18 @@ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) > > void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) > { > + u64 overrun; > + > lockdep_assert_held(&cfs_b->lock); > > - if (!cfs_b->period_active) { > - cfs_b->period_active = 1; > - hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); > - hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); > - } > + if (cfs_b->period_active) > + return; > + > + cfs_b->period_active = 1; > + overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); > + cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period); > + cfs_b->expires_seq++; > + hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); > } > > static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
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