Re: [PATCH 2/2] sched: add statistic for rq->max_idle_balance_cost

From: Peter Zijlstra
Date: Thu Jan 23 2014 - 04:55:24 EST


On Thu, Jan 23, 2014 at 02:49:25PM +0800, Alex Shi wrote:
> On 01/23/2014 02:10 AM, Jason Low wrote:
> >>> > > P64(avg_idle);
> >>> > > + P64(max_idle_balance_cost);
> >>> > > #endif
> >>> > > P(ttwu_count);
> >> >
> >> > Not also the per-sd value in sd_alloc_ctl_domain_table() ?
> > Yeah, tracking the sd->max_newidle_lb_cost can also be useful.
> >
> >
>
> Thanks for suggestion!
>
> I thought the sd->max_newidle_lb_cost keep changing. But yes, it's
> still meaningful.
> BTW, in the pandaboard ES, sd balance cost is about 1~2ms.

That's an insane amount of time for only 2 cpus.

> ---
>
> From d37e712b623fb6776d0caba8e4bd06460e26b84e Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@xxxxxxxxxx>
> Date: Tue, 21 Jan 2014 13:28:55 +0800
> Subject: [PATCH] sched: add statistic for newidle load balance cost
>
> Tracking rq->max_idle_balance_cost and sd->max_newidle_lb_cost
> It's useful to track these values in debug mode.
>
> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxx>
> ---
> kernel/sched/core.c | 7 +++++--
> kernel/sched/debug.c | 1 +
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c3f3824..a046bc3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4293,7 +4293,7 @@ set_table_entry(struct ctl_table *entry,
> static struct ctl_table *
> sd_alloc_ctl_domain_table(struct sched_domain *sd)
> {
> - struct ctl_table *table = sd_alloc_ctl_entry(8);
> + struct ctl_table *table = sd_alloc_ctl_entry(9);

tip/master has 13 there, not 8.
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