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Date: Tue, 26 Nov 2013 13:35:59 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Alex Shi <alex.shi@...aro.org>, mingo@...hat.com,
peterz@...radead.org, morten.rasmussen@....com,
vincent.guittot@...aro.org, fweisbec@...il.com,
linux@....linux.org.uk, tony.luck@...el.com, fenghua.yu@...el.com,
tglx@...utronix.de, akpm@...ux-foundation.org,
arjan@...ux.intel.com, pjt@...gle.com, fengguang.wu@...el.com
CC: james.hogan@...tec.com, jason.low2@...com,
gregkh@...uxfoundation.org, hanjun.guo@...aro.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] sched: remove cpu_load decay.
On 11/24/2013 06:29 AM, Alex Shi wrote:
> On 11/22/2013 08:13 PM, Daniel Lezcano wrote:
>>
>> Hi Alex,
>>
>> I tried on my Xeon server (2 x 4 cores) your patchset and got the
>> following result:
>>
>> kernel a5d6e63323fe7799eb0e6 / + patchset
>>
>> hackbench -T -s 4096 -l 1000 -g 10 -f 40
>> 27.604 38.556
>
> Wondering if the following patch is helpful on your Xeon server?
>
> Btw, you can run vmstat as background tool or use 'perf sched'
> to get scheduler statistics change for this patchset.
>
> The following are results of original kernel and all 5 patches
> on pandaboard ES.
>
> latest kernel 527d1511310a89 + this patchset
> hackbench -T -g 10 -f 40
> 23.25" 20.79"
> 23.16" 20.4"
> 24.24" 20.29"
> hackbench -p -g 10 -f 40
> 26.52" 21.2"
> 23.89" 24.07"
> 25.65" 20.30"
> hackbench -P -g 10 -f 40
> 20.14" 19.53"
> 19.96" 20.37"
> 21.76" 20.39"
>
Here the new results with your patchset + patch #5
I have some issues with perf for the moment, so I will fix it up and
send the result after.
527d1511310a / + patchset + #5
hackbench -T -s 4096 -l 1000 -g 10 -f 40
26.677 30.308
27.914 28.497
28.390 30.360
28.048 28.587
26.344 29.513
27.848 28.706
28.315 30.152
28.232 29.721
26.549 28.766
30.340 38.801
hackbench -p -s 4096 -l 1000 -g 10 -f 40
34.522 35.469
34.545 34.966
34.469 35.342
34.115 35.286
34.457 35.592
34.561 35.314
34.459 35.316
34.054 35.629
34.532 35.149
34.459 34.876
hackbench -P -s 4096 -l 1000 -g 10 -f 40
38.938 30.308
39.363 28.497
39.340 30.360
38.909 28.587
39.095 29.513
38.869 28.706
39.041 30.152
38.939 29.721
38.992 28.766
38.947 38.801
> ------
> From 4f5efd6c2b1e7293410ad57c3db24dcf3394c4a3 Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@...aro.org>
> Date: Sat, 23 Nov 2013 23:18:09 +0800
> Subject: [PATCH] sched: aggravate target cpu load to reduce task moving
>
> Task migration happens when target just a bit less then source cpu load
> to reduce such situation happens, aggravate the target cpu with sd->
> imbalance_pct.
>
> Signed-off-by: Alex Shi <alex.shi@...aro.org>
> ---
> kernel/sched/fair.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index bccdd89..c49b7ba 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -978,7 +978,7 @@ static inline unsigned long group_weight(struct task_struct *p, int nid)
>
> static unsigned long weighted_cpuload(const int cpu);
> static unsigned long source_load(int cpu);
> -static unsigned long target_load(int cpu);
> +static unsigned long target_load(int cpu, int imbalance_pct);
> static unsigned long power_of(int cpu);
> static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
>
> @@ -3809,11 +3809,17 @@ static unsigned long source_load(int cpu)
> * Return a high guess at the load of a migration-target cpu weighted
> * according to the scheduling class and "nice" value.
> */
> -static unsigned long target_load(int cpu)
> +static unsigned long target_load(int cpu, int imbalance_pct)
> {
> struct rq *rq = cpu_rq(cpu);
> unsigned long total = weighted_cpuload(cpu);
>
> + /*
> + * without cpu_load decay, in most of time cpu_load is same as total
> + * so we need to make target a bit heavier to reduce task migration
> + */
> + total = total * imbalance_pct / 100;
> +
> if (!sched_feat(LB_BIAS))
> return total;
>
> @@ -4033,7 +4039,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
> this_cpu = smp_processor_id();
> prev_cpu = task_cpu(p);
> load = source_load(prev_cpu);
> - this_load = target_load(this_cpu);
> + this_load = target_load(this_cpu, 100);
>
> /*
> * If sync wakeup then subtract the (maximum possible)
> @@ -4089,7 +4095,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>
> if (balanced ||
> (this_load <= load &&
> - this_load + target_load(prev_cpu) <= tl_per_task)) {
> + this_load + target_load(prev_cpu, 100) <= tl_per_task)) {
> /*
> * This domain has SD_WAKE_AFFINE and
> * p is cache cold in this domain, and
> @@ -4135,7 +4141,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
> if (local_group)
> load = source_load(i);
> else
> - load = target_load(i);
> + load = target_load(i, sd->imbalance_pct);
>
> avg_load += load;
> }
> @@ -5478,7 +5484,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>
> /* Bias balancing toward cpus of our domain */
> if (local_group)
> - load = target_load(i);
> + load = target_load(i, env->sd->imbalance_pct);
> else
> load = source_load(i);
>
>
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