Messages in this thread Patch in this message |  | | From | Alex Shi <> | Subject | [patch v4 05/18] sched: quicker balancing on fork/exec/wake | Date | Thu, 24 Jan 2013 11:06:47 +0800 |
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Guess the search cpu from bottom to up in domain tree come from commit 3dbd5342074a1e sched: multilevel sbe sbf, the purpose is balancing over tasks on all level domains.
This balancing cost too much if there has many domain/groups in a large system.
If we remove this code, we will get quick fork/exec/wake with a similar balancing result amony whole system.
This patch increases 10+% performance of hackbench on my 4 sockets SNB machines and about 3% increasing on 2 sockets servers.
Signed-off-by: Alex Shi <alex.shi@intel.com> --- kernel/sched/fair.c | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ecfbf8e..895a3f4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3364,15 +3364,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) goto unlock; } - while (sd) { + if (sd) { int load_idx = sd->forkexec_idx; struct sched_group *group; - int weight; - - if (!(sd->flags & sd_flag)) { - sd = sd->child; - continue; - } if (sd_flag & SD_BALANCE_WAKE) load_idx = sd->wake_idx; @@ -3382,18 +3376,6 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) goto unlock; new_cpu = find_idlest_cpu(group, p, cpu); - - /* Now try balancing at a lower domain level of new_cpu */ - cpu = new_cpu; - weight = sd->span_weight; - sd = NULL; - for_each_domain(cpu, tmp) { - if (weight <= tmp->span_weight) - break; - if (tmp->flags & sd_flag) - sd = tmp; - } - /* while loop will break here if sd == NULL */ } unlock: rcu_read_unlock(); -- 1.7.12
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