Messages in this thread | | | Date | Wed, 20 Jan 2016 10:41:04 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH 2/4] sched: Consolidate nohz CPU load update code |
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On Tue, Jan 19, 2016 at 05:49:34PM +0100, Frederic Weisbecker wrote: > On Thu, Jan 14, 2016 at 02:18:40PM +0900, Byungchul Park wrote: > > On Wed, Jan 13, 2016 at 05:01:29PM +0100, Frederic Weisbecker wrote: > > > #ifdef CONFIG_NO_HZ_COMMON > > > +static void __update_cpu_load_nohz(struct rq *this_rq, > > > + unsigned long curr_jiffies, > > > > Do we need to pass current jiffies as a function parameter? > > I guess we don't, I just wasn't much sure of the possible overhead of READ_ONCE()
Ah. But I think passing an additional argument can cause additional overhead, too, e.g. additional store/load on stack. But I am not sure which one is larger, and it depends on architecture and abi.
> > > > > > + unsigned long load, > > > + int active) > > > +{ > > > + unsigned long pending_updates; > > > + > > > + pending_updates = curr_jiffies - this_rq->last_load_update_tick; > > > + if (pending_updates) { > > > + this_rq->last_load_update_tick = curr_jiffies; > > > + /* > > > + * In the regular NOHZ case, we were idle, this means load 0. > > > + * In the NOHZ_FULL case, we were non-idle, we should consider > > > + * its weighted load. > > > + */ > > > + __update_cpu_load(this_rq, load, pending_updates, active); > > > + } > > > +}
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