Messages in this thread | | | From | Vincent Guittot <> | Date | Mon, 3 Jun 2019 11:53:50 +0200 | Subject | Re: [PATCH] sched/fair: Cleanup definition of NOHZ blocked load functions |
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On Mon, 3 Jun 2019 at 11:38, Peter Zijlstra <peterz@infradead.org> wrote: > > On Sun, Jun 02, 2019 at 05:41:10PM +0100, Valentin Schneider wrote: > > cfs_rq_has_blocked() and others_have_blocked() are only used within > > update_blocked_averages(). The !CONFIG_FAIR_GROUP_SCHED version of the > > latter calls them within a #define CONFIG_NO_HZ_COMMON block, whereas > > the CONFIG_FAIR_GROUP_SCHED one calls them unconditionnally. > > > > As reported by Qian, the above leads to this warning in > > !CONFIG_NO_HZ_COMMON configs: > > > > kernel/sched/fair.c: In function 'update_blocked_averages': > > kernel/sched/fair.c:7750:7: warning: variable 'done' set but not used > > [-Wunused-but-set-variable] > > > > It wouldn't be wrong to keep cfs_rq_has_blocked() and > > others_have_blocked() as they are, but since their only current use is > > to figure out when we can stop calling update_blocked_averages() on > > fully decayed NOHZ idle CPUs, we can give them a new definition for > > !CONFIG_NO_HZ_COMMON. > > > > Change the definition of cfs_rq_has_blocked() and > > others_have_blocked() for !CONFIG_NO_HZ_COMMON so that the > > NOHZ-specific blocks of update_blocked_averages() become no-ops and > > the 'done' variable gets optimised out. > > > > No change in functionality intended. > > > > Reported-by: Qian Cai <cai@lca.pw> > > Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> > > I'm thinking the below can go on top to further clean up?
For both patches Acked-by: Vincent Guittot <vincent.guitto@linaro.org>
> > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7722,9 +7722,18 @@ static inline bool others_have_blocked(s > > return false; > } > + > +static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) > +{ > + rq->last_blocked_load_update_tick = jiffies; > + > + if (!has_blocked) > + rq->has_blocked_load = 0; > +} > #else > static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; } > static inline bool others_have_blocked(struct rq *rq) { return false; } > +static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {} > #endif > > #ifdef CONFIG_FAIR_GROUP_SCHED > @@ -7746,18 +7755,6 @@ static inline bool cfs_rq_is_decayed(str > return true; > } > > -#ifdef CONFIG_NO_HZ_COMMON > -static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) > -{ > - rq->last_blocked_load_update_tick = jiffies; > - > - if (!has_blocked) > - rq->has_blocked_load = 0; > -} > -#else > -static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {} > -#endif > - > static void update_blocked_averages(int cpu) > { > struct rq *rq = cpu_rq(cpu); > @@ -7870,11 +7867,7 @@ static inline void update_blocked_averag > update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class); > update_dl_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &dl_sched_class); > update_irq_load_avg(rq, 0); > -#ifdef CONFIG_NO_HZ_COMMON > - rq->last_blocked_load_update_tick = jiffies; > - if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq)) > - rq->has_blocked_load = 0; > -#endif > + update_blocked_load_status(rq, cfs_rq_has_blocked(cfs_rq) || others_have_blocked(rq)); > rq_unlock_irqrestore(rq, &rf); > } >
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