Messages in this thread Patch in this message | | | From | Vaidyanathan Srinivasan <> | Subject | [RFC PATCH v4 3/7] sched: nominate preferred wakeup cpu | Date | Fri, 21 Nov 2008 14:01:14 +0530 |
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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 + }; /* @@ -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 @@ -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); return group_min; } #endif
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