Messages in this thread | | | Subject | Re: [LKP] [sched/fair] 070f5e860e: reaim.jobs_per_min -10.5% regression | From | Xing Zhengjun <> | Date | Fri, 19 Jun 2020 12:55:53 +0800 |
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On 6/17/2020 10:57 PM, Vincent Guittot wrote: > Le mercredi 17 juin 2020 à 08:30:21 (+0800), Xing Zhengjun a écrit : >> >> >> On 6/16/2020 2:54 PM, Vincent Guittot wrote: >>> >>> Hi Xing, >>> >>> Le mardi 16 juin 2020 à 11:17:16 (+0800), Xing Zhengjun a écrit : >>>> >>>> >>>> On 6/15/2020 4:10 PM, Vincent Guittot wrote: >>>>> Hi Xing, >>>>> >>>>> Le lundi 15 juin 2020 à 15:26:59 (+0800), Xing Zhengjun a écrit : >>>>>> >>>>>> >>>>>> On 6/12/2020 7:06 PM, Hillf Danton wrote: >>>>>>> >>>>>>> On Fri, 12 Jun 2020 14:36:49 +0800 Xing Zhengjun wrote: >>>>> >>> >>> ... >>> >>>>> >>>> >>>> I apply the patch based on v5.7, the test result is as the following: >>> >>> TBH, I didn't expect that the results would still be bad, so i wonder if the threshold are >>> the root problem. >>> >>> Could you run tests with the patch below that removes condition with runnable_avg ? >>> I just want to make sure that those 2 conditions are the root cause. >>> >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>> index da3e5b54715b..f5774d0af059 100644 >>> --- a/kernel/sched/fair.c >>> +++ b/kernel/sched/fair.c >>> @@ -8210,10 +8210,6 @@ group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs) >>> if (sgs->sum_nr_running < sgs->group_weight) >>> return true; >>> >>> - if ((sgs->group_capacity * imbalance_pct) < >>> - (sgs->group_runnable * 100)) >>> - return false; >>> - >>> if ((sgs->group_capacity * 100) > >>> (sgs->group_util * imbalance_pct)) >>> return true; >>> @@ -8239,10 +8235,6 @@ group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs) >>> (sgs->group_util * imbalance_pct)) >>> return true; >>> >>> - if ((sgs->group_capacity * imbalance_pct) < >>> - (sgs->group_runnable * 100)) >>> - return true; >>> - >>> return false; >>> } >>> >>> >>> >>> Thanks. >>> Vincent >>> >> >> >> I apply the patch based on v5.7, the test result is as the following: >> >> ========================================================================================= >> tbox_group/testcase/rootfs/kconfig/compiler/runtime/nr_task/debug-setup/test/cpufreq_governor/ucode: >> >> lkp-ivb-d04/reaim/debian-x86_64-20191114.cgz/x86_64-rhel-7.6/gcc-7/300s/100%/test/five_sec/performance/0x21 >> >> commit: >> 9f68395333ad7f5bfe2f83473fed363d4229f11c >> 070f5e860ee2bf588c99ef7b4c202451faa48236 >> v5.7 >> 63a5d0fbb5ec62f5148c251c01e709b8358cd0ee (the test patch) >> >> 9f68395333ad7f5b 070f5e860ee2bf588c99ef7b4c2 v5.7 >> 63a5d0fbb5ec62f5148c251c01e >> ---------------- --------------------------- --------------------------- >> --------------------------- >> %stddev %change %stddev %change %stddev %change >> %stddev >> \ | \ | \ >> | \ >> 0.69 -10.3% 0.62 -9.1% 0.62 >> +1.0% 0.69 reaim.child_systime >> 0.62 -1.0% 0.61 +0.5% 0.62 >> -0.1% 0.62 reaim.child_utime >> 66870 -10.0% 60187 -7.6% 61787 >> +1.1% 67636 reaim.jobs_per_min >> 16717 -10.0% 15046 -7.6% 15446 >> +1.1% 16909 reaim.jobs_per_min_child > > OK. So the regression disappears when the conditions on runnable_avg are removed. > > In the meantime, I have been able to understand more deeply what was happeningi > for this bench and how it is impacted by > commit: 070f5e860ee2 ("sched/fair: Take into account runnable_avg to classify group") > > This bench forks a new thread for each and every new step. But a newly forked > threads start with a load_avg and a runnable_avg set to max whereas the threads > are running shortly before exiting. This makes the CPU to be set overloaded in > some case whereas it isn't. > > Could you try the patch below ? > It fixes the problem on my setup (I have finally been able to reproduce the problem) > > --- > kernel/sched/fair.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 0aeffff62807..b33a4a9e1491 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -807,7 +807,7 @@ void post_init_entity_util_avg(struct task_struct *p) > } > } > > - sa->runnable_avg = cpu_scale; > + sa->runnable_avg = sa->util_avg; > > if (p->sched_class != &fair_sched_class) { > /* >
I apply the patch above based on v5.7, the test result is as the following:
========================================================================================= tbox_group/testcase/rootfs/kconfig/compiler/runtime/nr_task/debug-setup/test/cpufreq_governor/ucode: lkp-ivb-d04/reaim/debian-x86_64-20191114.cgz/x86_64-rhel-7.6/gcc-7/300s/100%/test/five_sec/performance/0x21
commit: 9f68395333ad7f5bfe2f83473fed363d4229f11c 070f5e860ee2bf588c99ef7b4c202451faa48236 v5.7 cbb4d668e7431479a7978fa79d64c2271adefab0 ( the test patch which modify post_init_entity_util_avg())
9f68395333ad7f5b 070f5e860ee2bf588c99ef7b4c2 v5.7 cbb4d668e7431479a7978fa79d6 ---------------- --------------------------- --------------------------- --------------------------- %stddev %change %stddev %change %stddev %change %stddev \ | \ | \ | \ 0.69 -10.3% 0.62 -9.1% 0.62 +0.6% 0.69 reaim.child_systime 0.62 -1.0% 0.61 +0.5% 0.62 -0.3% 0.62 reaim.child_utime 66870 -10.0% 60187 -7.6% 61787 +0.7% 67335 reaim.jobs_per_min 16717 -10.0% 15046 -7.6% 15446 +0.7% 16833 reaim.jobs_per_min_child 97.84 -1.1% 96.75 -0.4% 97.43 +0.2% 98.05 reaim.jti 72000 -10.8% 64216 -8.3% 66000 +0.0% 72000 reaim.max_jobs_per_min 0.36 +10.6% 0.40 +7.8% 0.39 -0.6% 0.36 reaim.parent_time 1.58 ± 2% +71.0% 2.70 ± 2% +26.9% 2.01 ± 2% -8.8% 1.44 ± 2% reaim.std_dev_percent 0.00 ± 5% +110.4% 0.01 ± 3% +48.8% 0.01 ± 7% -24.6% 0.00 ± 7% reaim.std_dev_time 50800 -2.4% 49600 -1.6% 50000 +0.0% 50800 reaim.workload
-- Zhengjun Xing
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