Messages in this thread | | | From | Paul Turner <> | Date | Sat, 24 Aug 2013 03:33:59 -0700 | Subject | Re: [PATCH 07/10] sched, fair: Optimize find_busiest_queue() |
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On Mon, Aug 19, 2013 at 9:01 AM, Peter Zijlstra <peterz@infradead.org> wrote: > Use for_each_cpu_and() and thereby avoid computing the capacity for > CPUs we know we're not interested in. > > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > --- > kernel/sched/fair.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4977,7 +4977,7 @@ static struct rq *find_busiest_queue(str > unsigned long busiest_load = 0, busiest_power = SCHED_POWER_SCALE; > int i; > > - for_each_cpu(i, sched_group_cpus(group)) { > + for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { > unsigned long power = power_of(i); > unsigned long capacity = DIV_ROUND_CLOSEST(power, > SCHED_POWER_SCALE); > @@ -4986,9 +4986,6 @@ static struct rq *find_busiest_queue(str > if (!capacity) > capacity = fix_small_capacity(env->sd, group); > > - if (!cpumask_test_cpu(i, env->cpus)) > - continue; > - > rq = cpu_rq(i); > wl = weighted_cpuload(i);
There's no need to actually do the divisions immediately below this also.
e.g. unsigned long max_load_power = SCHED_POWER_SCALE; ... if (wl * max_load_power > max_load * power) { max_load = wl; max_load_power = power; ...
This would actually end up being a little more accurate even.
[ Alternatively without caching max_load_power we could compare wl * power vs max_load * SCHED_POWER_SCALE. ]
Reviewed-by: Paul Turner <pjt@google.com>
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