Messages in this thread | | | From | Paul Turner <> | Date | Tue, 28 Jun 2011 19:29:03 -0700 | Subject | Re: [patch 07/16] sched: expire invalid runtime |
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On Mon, Jun 27, 2011 at 9:42 PM, Paul Turner <pjt@google.com> wrote: > On Wed, Jun 22, 2011 at 8:47 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: >> On Tue, 2011-06-21 at 00:16 -0700, Paul Turner wrote: >> >>> + now = sched_clock_cpu(smp_processor_id()); >>> + cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); >> >>> + if ((s64)(rq->clock - cfs_rq->runtime_expires) < 0) >> >> Is there a good reason to mix these two (related) time sources? >> > > It does make sense to remove the (current) aliasing dependency, will > use rq->clock for setting expiration. >
So looking more closely at this I think i prefer the "mix" after all.
Using rq->clock within __refill_cfs_bandwidth_runtime adds the requirement of taking rq->lock on the current cpu within the period timer so that we can update rq->clock (which then just gets set to sched_clock anyway).
Expiration logic is already dependent on the fact that rq->clock snapshots sched_clock (the 2ms bound on clock-to-clock drift). Given that this is an infrequent (once/period) operation I think it's better to leave it as an explicit sched_clock_cpu call, with an explanatory comment. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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