Messages in this thread | | | Date | Tue, 26 Nov 2013 13:35:59 +0100 | From | Daniel Lezcano <> | Subject | Re: [RFC PATCH 0/4] sched: remove cpu_load decay. |
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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@linaro.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@linaro.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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