lkml.org 
[lkml]   [2014]   [Aug]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [sched] 143e1e28cb4: +17.9% aim7.jobs-per-min, -9.7% hackbench.throughput
On 11 August 2014 15:33, Peter Zijlstra <peterz@infradead.org> wrote:

[snip]

>
>
> Now I think I see why this is; we've reduced load balancing frequency
> significantly on this machine due to:

I agree with you about the root cause

>
>
> -#define SD_SIBLING_INIT (struct sched_domain) { \
> - .min_interval = 1, \
> - .max_interval = 2, \
>
>
> -#define SD_MC_INIT (struct sched_domain) { \
> - .min_interval = 1, \
> - .max_interval = 4, \
>
>
> -#define SD_CPU_INIT (struct sched_domain) { \
> - .min_interval = 1, \
> - .max_interval = 4, \
>
>
> *sd = (struct sched_domain){
> .min_interval = sd_weight,
> .max_interval = 2*sd_weight,
>
> Which both increased the min and max value significantly for all domains
> involved.
>
> That said; I think we might want to do something like the below; I can
> imagine decreasing load balancing too much will negatively impact other
> workloads.
>
> Maybe slightly modified to make sure the first domain has a min_interval
> of 1.
>
> ---
> kernel/sched/core.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1211575a2208..67ed5d854da1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6049,8 +6049,8 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
> sd_flags &= ~TOPOLOGY_SD_FLAGS;
>
> *sd = (struct sched_domain){
> - .min_interval = sd_weight,
> - .max_interval = 2*sd_weight,
> + .min_interval = max(1, sd_weight/2),
> + .max_interval = sd_weight,

What about using ilog2 like the default scaling mode of other
scheduler tunables ?

Regards,
Vincent

> .busy_factor = 32,
> .imbalance_pct = 125,
>
> @@ -6076,7 +6076,7 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
> ,
>
> .last_balance = jiffies,
> - .balance_interval = sd_weight,
> + .balance_interval = max(1, sd_weight/2),
> .smt_gain = 0,
> .max_newidle_lb_cost = 0,
> .next_decay_max_lb_cost = jiffies,


\
 
 \ /
  Last update: 2014-08-25 16:01    [W:2.147 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site