On 28/04/20 23:33, Scott Wood wrote: > On Tue, 2020-04-28 at 22:37 +0100, Valentin Schneider wrote: >> On 28/04/20 06:02, Scott Wood wrote: >> > Thus, newidle_balance() is entered with interrupts enabled, which allows >> > (in the next patch) enabling interrupts when the lock is dropped. >> > >> > Signed-off-by: Scott Wood <swood@xxxxxxxxxx> >> > --- >> > kernel/sched/core.c | 7 ++++--- >> > kernel/sched/fair.c | 45 ++++++++++++++++---------------------------- >> > kernel/sched/sched.h | 6 ++---- >> > 3 files changed, 22 insertions(+), 36 deletions(-) >> > >> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> > index 9a2fbf98fd6f..0294beb8d16c 100644 >> > --- a/kernel/sched/core.c >> > +++ b/kernel/sched/core.c >> > @@ -3241,6 +3241,10 @@ static struct rq *finish_task_switch(struct >> > task_struct *prev) >> > } >> > >> > tick_nohz_task_switch(); >> > + >> > + if (is_idle_task(current)) >> > + newidle_balance(); >> > + >> >> This means we must go through a switch_to(idle) before figuring out we >> could've switched to a CFS task, and do it then. I'm curious to see the >> performance impact of that. > > Any particular benchmark I should try? > I'm going to be very original and suggest hackbench :-) That would just be the first stop however, you would also want to try something less wakeup-intensive, maybe sysbench and the like - I'm thinking if you spawn ~1.5*nr_cpu_ids CPU-hogs, you'll hit that double switch fairly easily. And then there's always the big boys benchmarks like specjbb and co - I'd suggest having a look at Mel's mmtests.
