Messages in this thread | | | Date | Fri, 17 Jan 2014 16:09:39 +0100 | From | Daniel Lezcano <> | Subject | Re: [PATCH 4/4] sched: Idle task shortcut optimization |
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On 01/17/2014 03:09 PM, Peter Zijlstra wrote: > On Fri, Jan 17, 2014 at 10:04:04AM +0100, Daniel Lezcano wrote: >> + schedstat_inc(rq, sched_goidle); >> +#ifdef CONFIG_SMP >> + /* Trigger the post schedule to do an idle_enter for CFS */ >> + rq->post_schedule = 1; >> +#endif >> + return rq->idle; > > Urgh, that retains the stupid idle crap like it is. > > I've not yet tested this, but is there a reason something like the below > couldn't work?
I tested it by running hackbench and it seems to work as expected.
> --- > Subject: sched: Clean up idle task SMP logic > From: Peter Zijlstra <peterz@infradead.org> > Date: Fri Jan 17 14:54:02 CET 2014 > > The idle post_schedule hook is just a vile waste of time, fix it proper. > > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > --- > kernel/sched/fair.c | 5 +++-- > kernel/sched/idle_task.c | 21 ++++++--------------- > 2 files changed, 9 insertions(+), 17 deletions(-) > > Index: linux-2.6/kernel/sched/fair.c > =================================================================== > --- linux-2.6.orig/kernel/sched/fair.c > +++ linux-2.6/kernel/sched/fair.c > @@ -2416,7 +2416,8 @@ void idle_exit_fair(struct rq *this_rq) > update_rq_runnable_avg(this_rq, 0); > } > > -#else > +#else /* CONFIG_SMP */ > + > static inline void update_entity_load_avg(struct sched_entity *se, > int update_cfs_rq) {} > static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} > @@ -2428,7 +2429,7 @@ static inline void dequeue_entity_load_a > int sleep) {} > static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, > int force_update) {} > -#endif > +#endif /* CONFIG_SMP */ > > static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) > { > Index: linux-2.6/kernel/sched/idle_task.c > =================================================================== > --- linux-2.6.orig/kernel/sched/idle_task.c > +++ linux-2.6/kernel/sched/idle_task.c > @@ -13,18 +13,8 @@ select_task_rq_idle(struct task_struct * > { > return task_cpu(p); /* IDLE tasks as never migrated */ > } > - > -static void pre_schedule_idle(struct rq *rq, struct task_struct *prev) > -{ > - idle_exit_fair(rq); > - rq_last_tick_reset(rq); > -} > - > -static void post_schedule_idle(struct rq *rq) > -{ > - idle_enter_fair(rq); > -} > #endif /* CONFIG_SMP */ > + > /* > * Idle tasks are unconditionally rescheduled: > */ > @@ -37,8 +27,7 @@ static struct task_struct *pick_next_tas > { > schedstat_inc(rq, sched_goidle); > #ifdef CONFIG_SMP > - /* Trigger the post schedule to do an idle_enter for CFS */ > - rq->post_schedule = 1; > + idle_enter_fair(rq); > #endif > return rq->idle; > } > @@ -58,6 +47,10 @@ dequeue_task_idle(struct rq *rq, struct > > static void put_prev_task_idle(struct rq *rq, struct task_struct *prev) > { > +#ifdef CONFIG_SMP > + idle_exit_fair(rq); > + rq_last_tick_reset(rq); > +#endif > } > > static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued) > @@ -101,8 +94,6 @@ const struct sched_class idle_sched_clas > > #ifdef CONFIG_SMP > .select_task_rq = select_task_rq_idle, > - .pre_schedule = pre_schedule_idle, > - .post_schedule = post_schedule_idle, > #endif > > .set_curr_task = set_curr_task_idle, >
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