Messages in this thread | | | Subject | Re: [RFC PATCH v4 3/7] sched: nominate preferred wakeup cpu | From | Peter Zijlstra <> | Date | Sun, 23 Nov 2008 03:03:58 +0100 |
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On Fri, 2008-11-21 at 14:01 +0530, Vaidyanathan Srinivasan wrote: > When the system utilisation is low and more cpus are idle, > then the process waking up from sleep should prefer to > wakeup an idle cpu from semi-idle cpu package (multi core > package) rather than a completely idle cpu package which > would waste power. > > Use the sched_mc balance logic in find_busiest_group() to > nominate a preferred wakeup cpu. > > This info can be sored in appropriate sched_domain, but > updating this info in all copies of sched_domain is not > practical. Hence this information is stored in root_domain > struct which is one copy per partitioned sched domain. > The root_domain can be accessed from each cpu's runqueue > and there is one copy per partitioned sched domain. > > Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> > --- > > kernel/sched.c | 15 +++++++++++++++ > 1 files changed, 15 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 79b71f3..d28cd98 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -493,6 +493,17 @@ struct root_domain { > #ifdef CONFIG_SMP > struct cpupri cpupri; > #endif > +#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) > + > + /* > + * Preferred wake up cpu nominated by sched_mc balance that will be > + * used when most cpus are idle in the system indicating overall very > + * low system utilisation. Triggered at POWERSAVINGS_BALANCE_WAKEUP(2) > + */ > + unsigned int sched_mc_preferred_wakeup_cpu; > + > +#endif > + > }; > > /*
Do we really need that extra whitespace?
> @@ -3090,6 +3101,7 @@ static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest, > return 0; > } > > + > /* > * find_busiest_group finds and returns the busiest CPU group within the > * domain. It calculates and returns the amount of weighted load which
Ditto?
> @@ -3406,6 +3418,9 @@ out_balanced: > > if (this == group_leader && group_leader != group_min) { > *imbalance = min_load_per_task; > + if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) > + cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu = > + first_cpu(group_leader->cpumask);
While not strictly needed, I prefer braces around multi-line statments. It's easier on the eyes.
> return group_min; > } > #endif >
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