On 04/02/2013 03:23 PM, Michael Wang wrote:
> | 15 GB | 12 | 45393 | | 43986 |
> | 15 GB | 16 | 45110 | | 45719 |
> | 15 GB | 24 | 41415 | | 36813 | -11.11%
> | 15 GB | 32 | 35988 | | 34025 |
>
> The reason may caused by wake_affine()'s higher overhead, and pgbench is
> really sensitive to this stuff...
Michael:
I changed the threshold to 0.1ms it has same effect on aim7.
So could you try the following on pgbench?
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index bf8086b..a3c3d43 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -53,6 +53,7 @@ extern unsigned int sysctl_numa_balancing_settle_count;
#ifdef CONFIG_SCHED_DEBUG
extern unsigned int sysctl_sched_migration_cost;
+extern unsigned int sysctl_sched_burst_threshold;
extern unsigned int sysctl_sched_nr_migrate;
extern unsigned int sysctl_sched_time_avg;
extern unsigned int sysctl_timer_migration;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index dbaa8ca..dd5a324 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -91,6 +91,7 @@ unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
+const_debug unsigned int sysctl_sched_burst_threshold = 100000UL;
/*
* The exponential sliding window over which load is averaged for shares
@@ -3103,12 +3104,24 @@ static int wake_affine(struct sched_domain *sd, struct
task_struct *p, int sync)
unsigned long weight;
int balanced;
int runnable_avg;
+ int burst = 0;
idx = sd->wake_idx;
this_cpu = smp_processor_id();
prev_cpu = task_cpu(p);
- load = source_load(prev_cpu, idx);
- this_load = target_load(this_cpu, idx);
+
+ if (cpu_rq(this_cpu)->avg_idle < sysctl_sched_burst_threshold ||
+ cpu_rq(prev_cpu)->avg_idle < sysctl_sched_burst_threshold)
+ burst= 1;
+
+ /* use instant load for bursty waking up */
+ if (!burst) {
+ load = source_load(prev_cpu, idx);
+ this_load = target_load(this_cpu, idx);
+ } else {
+ load = cpu_rq(prev_cpu)->load.weight;
+ this_load = cpu_rq(this_cpu)->load.weight;
+ }
/*
* If sync wakeup then subtract the (maximum possible)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index afc1dc6..1f23457 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -327,6 +327,13 @@ static struct ctl_table kern_table[] = {
.proc_handler = proc_dointvec,
},
{
+ .procname = "sched_burst_threshold_ns",
+ .data = &sysctl_sched_burst_threshold,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
.procname = "sched_nr_migrate",
.data = &sysctl_sched_nr_migrate,
.maxlen = sizeof(unsigned int),
--
Thanks Alex
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