Messages in this thread | | | Date | Thu, 18 Dec 2008 23:42:10 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH v7 4/8] sched: nominate preferred wakeup cpu |
| |
* Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> [2008-12-18 23:26:22]:
> 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 | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 0b9bbbd..3415fa3 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -493,6 +493,14 @@ 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 > }; > > /* > @@ -3407,6 +3415,10 @@ 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); > + } > return group_min; > } > #endif
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
-- Balbir
| |