Messages in this thread Patch in this message | | | From | Gautham R Shenoy <> | Subject | [RFC PATCH 2 2/2] sched: Nominate a power-efficient ilb in select_nohz_balancer() | Date | Tue, 14 Apr 2009 10:25:35 +0530 |
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The CPU that first goes idle becomes the idle-load-balancer and remains that until either it picks up a task or till all the CPUs of the system goes idle.
Optimize this further to allow it to relinquish it's post once all it's siblings in the power-aware sched_domain go idle, thereby allowing the whole package-core to go idle. While relinquising the post, nominate another an idle-load balancer from a semi-idle core/package.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> ---
kernel/sched.c | 18 +++++++++++++++++- 1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index d702be7..bbf367d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -4402,8 +4402,24 @@ int select_nohz_load_balancer(int stop_tick) /* make me the ilb owner */ if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1) return 1; - } else if (atomic_read(&nohz.load_balancer) == cpu) + } else if (atomic_read(&nohz.load_balancer) == cpu) { + int new_ilb; + + if (!(sched_smt_power_savings || + sched_mc_power_savings)) + return 1; + /* + * Check to see if there is a more power-efficient + * ilb. + */ + new_ilb = find_new_ilb(cpu); + if (new_ilb < nr_cpu_ids && new_ilb != cpu) { + atomic_set(&nohz.load_balancer, -1); + resched_cpu(new_ilb); + return 0; + } return 1; + } } else { if (!cpumask_test_cpu(cpu, nohz.cpu_mask)) return 0;
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