Messages in this thread | | | Date | Tue, 6 Mar 2018 20:02:41 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 1/4] sched/fair: add util_est on top of PELT |
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On Thu, Feb 22, 2018 at 05:01:50PM +0000, Patrick Bellasi wrote: > +struct util_est { > + unsigned int enqueued; > + unsigned int ewma; > +#define UTIL_EST_WEIGHT_SHIFT 2 > +};
> + ue = READ_ONCE(p->se.avg.util_est);
> + WRITE_ONCE(p->se.avg.util_est, ue);
That is actually quite dodgy... and relies on the fact that we have the 8 byte case in __write_once_size() and __read_once_size() unconditionally. It then further relies on the compiler DTRT for 32bit platforms, which is generating 2 32bit loads/stores.
The advantage is of course that it will use single u64 loads/stores where available.
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