On 04/03/2013 02:53 PM, Alex Shi wrote:
> On 04/03/2013 02:22 PM, Michael Wang wrote:
>>>>
>>>> If many tasks sleep long time, their runnable load are zero. And if they
>>>> are waked up bursty, too light runnable load causes big imbalance among
>>>> CPU. So such benchmark, like aim9 drop 5~7%.
>>>>
>>>> With this patch the losing is covered, and even is slight better.
>> A fast test show the improvement disappear and the regression back
>> again...after applied this one as the 8th patch, it doesn't works.
>
> It always is good for on benchmark and bad for another. :)
That's right :)
>
> the following patch include the renamed knob, and you can tune it under
> /proc/sys/kernel/... to see detailed impact degree.
Could I make the conclusion that the improvement on pgbench was caused
by the new weighted_cpuload()?
The burst branch seems to just adopt the load in old world, if reduce
the rate to enter that branch could regain the benefit, then I could
confirm my supposition.
>
> + if (cpu_rq(this_cpu)->avg_idle < sysctl_sched_migration_cost ||
> + cpu_rq(prev_cpu)->avg_idle < sysctl_sched_migration_cost)
It should be 'sysctl_sched_burst_threshold' here, isn't it? anyway, I
will take a try with different rate.
Regards,
Michael Wang
> + 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),
>
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