Messages in this thread | | | Subject | Re: [CFS Bandwidth Control v4 5/7] sched: add exports tracking cfs bandwidth control statistics | From | Peter Zijlstra <> | Date | Fri, 25 Feb 2011 09:54:24 +0100 |
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On Thu, 2011-02-24 at 19:26 -0800, Paul Turner wrote: > On Wed, Feb 23, 2011 at 5:32 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > On Tue, 2011-02-15 at 19:18 -0800, Paul Turner wrote: > >> + raw_spin_lock(&cfs_b->lock); > >> + cfs_b->throttled_time += (rq->clock - cfs_rq->throttled_timestamp); > >> + raw_spin_unlock(&cfs_b->lock); > > > > That seems to put the cost of things on the wrong side. Read is rare, > > update is frequent, and you made the frequent thing the most expensive > > one. > > Hum.. the trade-off here is non-trivial I think > > - This update is only once per-quota period (*if* we throttled within > that period). This places the frequency in the 10s-100s of ms range. > - Sampling would probably occur on an order of once a second (assuming > some enterprise management system that cares about these statistics).
Ugh,. people are really polling state like that? If the event is rare pushing state is much saner.
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