Messages in this thread |  | | From | Vincent Guittot <> | Date | Tue, 9 Feb 2021 15:22:55 +0100 | Subject | Re: [RFC PATCH 5/6] sched/fair: trigger the update of blocked load on newly idle cpu |
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On Tue, 9 Feb 2021 at 14:47, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 05/02/2021 12:48, Vincent Guittot wrote: > > Instead of waking up a random and already idle CPU, we can take advantage > > of this_cpu being about to enter idle to run the ILB and update the > > blocked load. > > > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > --- > > include/linux/sched/nohz.h | 2 ++ > > kernel/sched/fair.c | 11 ++++++++--- > > kernel/sched/idle.c | 6 ++++++ > > 3 files changed, 16 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/sched/nohz.h b/include/linux/sched/nohz.h > > index 6d67e9a5af6b..74cdc4e87310 100644 > > --- a/include/linux/sched/nohz.h > > +++ b/include/linux/sched/nohz.h > > @@ -9,8 +9,10 @@ > > #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) > > extern void nohz_balance_enter_idle(int cpu); > > extern int get_nohz_timer_target(void); > > +extern void nohz_run_idle_balance(int cpu); > > #else > > static inline void nohz_balance_enter_idle(int cpu) { } > > +static inline void nohz_run_idle_balance(int cpu) { } > > #endif > > (1) Since nohz_run_idle_balance() would be an interface one sched class > (fair) exports to another (idle) I wonder if kernel/sched/sched.h would > be the more appropriate include file to export/define it?
Yes probably. I have been influenced by the "nohz" filename but kernel/sched/sched.h is better
> > nohz_balance_exit_idle() is exported via kernel/sched/sched.h (used only > within the scheduler) whereas nohz_balance_enter_idle() is exported via > include/linux/sched/nohz.h (used in kernel/time/tick-sched.c). > > Isn't include/linux/sched/nohz.h the interface between kernel/sched/ and > kernel/time? > > There is one exception already though: calc_load_nohz_remote() defined > in kernel/sched/loadavg.c and (only) used in kernel/sched/core.c. > > > (2) Is there a need for an extra function nohz_run_idle_balance()? > do_idle() could call nohz_idle_balance() directly in case in would be > exported instead.
I didn't want to expose the 2 parameters of nohz_idle_balance in do_idle() and especially the enum cpu_idle_type but it seems that it is already available so I can probably call nohz_idle_balance(cpu_rq(cpu), CPU_IDLE); directly
> > [...]
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