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 <c...@lca.pw> > Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com>
I'm thinking the below can go on top to further clean up? --- 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); }