Commit-ID: e0a79f529d5ba2507486d498b25da40911d95cf6 Gitweb: http://git.kernel.org/tip/e0a79f529d5ba2507486d498b25da40911d95cf6 Author: Mike Galbraith <bitbuc...@online.de> AuthorDate: Mon, 28 Jan 2013 12:19:25 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 4 Feb 2013 20:07:24 +0100
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 <bitbuc...@online.de> Cc: Peter Zijlstra <a.p.zijls...@chello.nl> Link: http://lkml.kernel.org/r/1359371965.5783.127.ca...@marge.simpson.net Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8dbee9f..ed18c74 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
