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| author | Mike Galbraith <bitbucket@online.de> | 2013-01-28 12:19:25 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-02-04 20:07:24 +0100 |
| commit | e0a79f529d5ba2507486d498b25da40911d95cf6 (patch) | |
| tree | 469947cd4407877ba69aa474cdfed0f2bda61d92 | |
| parent | sched/rt: Further simplify pick_rt_task() (diff) | |
| download | linux-e0a79f529d5ba2507486d498b25da40911d95cf6.tar.xz linux-e0a79f529d5ba2507486d498b25da40911d95cf6.zip | |
sched: Fix select_idle_sibling() bouncing cow syndrome
If the previous CPU is cache affine and idle, select it.
The current implementation simply traverses the sd_llc domain,
taking the first idle CPU encountered, which walks buddy pairs
hand in hand over the package, inflicting excruciating pain.
1 tbench pair (worst case) in a 10 core + SMT package:
pre 15.22 MB/sec 1 procs
post 252.01 MB/sec 1 procs
Signed-off-by: Mike Galbraith <bitbucket@online.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1359371965.5783.127.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/sched/fair.c | 21 |
1 files changed, 7 insertions, 14 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8dbee9f4ceb2..ed18c74db017 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3252,25 +3252,18 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) */ static int select_idle_sibling(struct task_struct *p, int target) { - int cpu = smp_processor_id(); - int prev_cpu = task_cpu(p); struct sched_domain *sd; struct sched_group *sg; - int i; + int i = task_cpu(p); - /* - * If the task is going to be woken-up on this cpu and if it is - * already idle, then it is the right target. - */ - if (target == cpu && idle_cpu(cpu)) - return cpu; + if (idle_cpu(target)) + return target; /* - * If the task is going to be woken-up on the cpu where it previously - * ran and if it is currently idle, then it the right target. + * If the prevous cpu is cache affine and idle, don't be stupid. */ - if (target == prev_cpu && idle_cpu(prev_cpu)) - return prev_cpu; + if (i != target && cpus_share_cache(i, target) && idle_cpu(i)) + return i; /* * Otherwise, iterate the domains and find an elegible idle cpu. @@ -3284,7 +3277,7 @@ static int select_idle_sibling(struct task_struct *p, int target) goto next; for_each_cpu(i, sched_group_cpus(sg)) { - if (!idle_cpu(i)) + if (i == target || !idle_cpu(i)) goto next; } |