Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance | From | Steven Sistare <> | Date | Mon, 19 Nov 2018 12:31:34 -0500 |
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On 11/9/2018 2:07 PM, Valentin Schneider wrote: > Hi Steve, > > On 09/11/2018 12:50, Steve Sistare wrote: >> Move the update of idle_stamp from idle_balance to the call site in >> pick_next_task_fair, to prepare for a future patch that adds work to >> pick_next_task_fair which must be included in the idle_stamp interval. >> No functional change. >> >> Signed-off-by: Steve Sistare <steven.sistare@oracle.com> >> --- >> kernel/sched/fair.c | 23 ++++++++++++++--------- >> 1 file changed, 14 insertions(+), 9 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 9031d39..da368ed 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3725,6 +3725,8 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) >> rq->misfit_task_load = task_h_load(p); >> } >> >> +#define IF_SMP(statement) statement >> + > > I'm not too hot on those IF_SMP() macros. Since you're not introducing > any other user for them, what about an inline function for rq->idle_stamp > setting ? When it's mapped to an empty statement (!CONFIG_SMP) GCC is > smart enough to remove the rq_clock() that would be passed to it on > CONFIG_SMP:
That may be true now, but I worry that rq_clock or its subroutines may gain side effects in the future that prevent the compiler from removing it. However, I could push rq_clock into the inline function:
static inline void rq_idle_stamp_set(rq) { rq->idle_stamp = rq_clock(rq); } static inline void rq_idle_stamp_clear(rq) { rq->idle_stamp = 0; }
I like that better, do you?
- Steve > ----->8----- > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c11adf3..34d9864 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3725,7 +3725,10 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) > rq->misfit_task_load = task_h_load(p); > } > > -#define IF_SMP(statement) statement > +static inline void set_rq_idle_stamp(struct rq *rq, u64 value) > +{ > + rq->idle_stamp = value; > +} > > static void overload_clear(struct rq *rq) > { > @@ -3772,7 +3775,7 @@ static inline int idle_balance(struct rq *rq, struct rq_flags *rf) > return 0; > } > > -#define IF_SMP(statement) /* empty */ > +static inline void set_rq_idle_stamp(struct rq *rq, u64 value) {} > > static inline void overload_clear(struct rq *rq) {} > static inline void overload_set(struct rq *rq) {} > @@ -6773,12 +6776,12 @@ done: __maybe_unused; > * We must set idle_stamp _before_ calling idle_balance(), such that we > * measure the duration of idle_balance() as idle time. > */ > - IF_SMP(rq->idle_stamp = rq_clock(rq);) > + set_rq_idle_stamp(rq, rq_clock(rq)); > > new_tasks = idle_balance(rq, rf); > > if (new_tasks) > - IF_SMP(rq->idle_stamp = 0;) > + set_rq_idle_stamp(rq, 0); > > /* > * Because idle_balance() releases (and re-acquires) rq->lock, it is >
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