Re: [LKP] [sched/fair] 070f5e860e: reaim.jobs_per_min -10.5% regression

Xing Zhengjun
2020-06-16T03:17:25Z

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:
>
> ...
>
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -8215,12 +8215,8 @@ group_has_capacity(unsigned int imbalanc
>>> 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))
>>> + if ((sgs->group_capacity * 100) > (sgs->group_util * imbalance_pct) &&
>>> + (sgs->group_capacity * 100) > (sgs->group_runnable * imbalance_pct))
>>> return true;
>>> return false;
>>> @@ -8240,12 +8236,8 @@ group_is_overloaded(unsigned int imbalan
>>> if (sgs->sum_nr_running <= sgs->group_weight)
>>> return false;
>>> - if ((sgs->group_capacity * 100) <
>>> - (sgs->group_util * imbalance_pct))
>>> - return true;
>>> -
>>> - if ((sgs->group_capacity * imbalance_pct) <
>>> - (sgs->group_runnable * 100))
>>> + if ((sgs->group_capacity * 100) < (sgs->group_util * imbalance_pct) ||
>>> + (sgs->group_capacity * 100) < (sgs->group_runnable * imbalance_pct))
>>> return true;
>>> return false;
>>>
>>
>> I apply the patch based on v5.7, the regression still existed.
>
> Thanks for the test. I don't know if it's relevant or not but the results seem a bit
> better with the patch and I'd like to check that it's only a matter of threshold to
> fix the problem.
>
> Could you try the patch below which is quite aggressive but will help to confirm this ?
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 28be1c984a42..3c51d557547b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8322,10 +8322,13 @@ static inline int sg_imbalanced(struct sched_group *group)
> static inline bool
> group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
> {
> + unsigned long imb;
> +
> if (sgs->sum_nr_running < sgs->group_weight)
> return true;
>
> - if ((sgs->group_capacity * imbalance_pct) <
> + imb = sgs->sum_nr_running * 100;
> + if ((sgs->group_capacity * imb) <
> (sgs->group_runnable * 100))
> return false;
>
> @@ -8347,6 +8350,8 @@ group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
> static inline bool
> group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
> {
> + unsigned long imb;
> +
> if (sgs->sum_nr_running <= sgs->group_weight)
> return false;
>
> @@ -8354,7 +8359,8 @@ 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) <
> + imb = sgs->sum_nr_running * 100;
> + if ((sgs->group_capacity * imb) <
> (sgs->group_runnable * 100))
> return true;
>
>

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
3e1643da53f3fc7414cfa3ad2a16ab2a164b7f4d (the test patch)

9f68395333ad7f5b 070f5e860ee2bf588c99ef7b4c2 v5.7
3e1643da53f3fc7414cfa3ad2a1
---------------- --------------------------- ---------------------------
---------------------------
%stddev %change %stddev %change
%stddev %change %stddev
\ | \ | \
| \
0.69 -10.3% 0.62 -9.1% 0.62
-7.1% 0.64 reaim.child_systime
0.62 -1.0% 0.61 +0.5% 0.62
+1.3% 0.63 reaim.child_utime
66870 -10.0% 60187 -7.6% 61787
-6.1% 62807 reaim.jobs_per_min
16717 -10.0% 15046 -7.6% 15446
-6.1% 15701 reaim.jobs_per_min_child
97.84 -1.1% 96.75 -0.4% 97.43
-0.5% 97.34 reaim.jti
72000 -10.8% 64216 -8.3% 66000
-5.7% 67885 reaim.max_jobs_per_min
0.36 +10.6% 0.40 +7.8% 0.39
+6.9% 0.38 reaim.parent_time
1.58 ± 2% +71.0% 2.70 ± 2% +26.9% 2.01 ±
2% +32.5% 2.09 ± 6% reaim.std_dev_percent
0.00 ± 5% +110.4% 0.01 ± 3% +48.8% 0.01 ±
7% +61.7% 0.01 ± 8% reaim.std_dev_time
50800 -2.4% 49600 -1.6% 50000
-1.3% 50133 reaim.workload

>>
>> =========================================================================================
>> 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
>> 6b33257768b8dd3982054885ea310871be2cfe0b (Hillf's patch)
>>
>> 9f68395333ad7f5b 070f5e860ee2bf588c99ef7b4c2 v5.7
>> 6b33257768b8dd3982054885ea3
>> ---------------- --------------------------- ---------------------------
>> ---------------------------
>> %stddev %change %stddev %change %stddev %change
>> %stddev
>> \ | \ | \
>> | \
>> 0.69 -10.3% 0.62 -9.1% 0.62
>> -10.1% 0.62 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
>> -8.3% 61305 reaim.jobs_per_min
>> 16717 -10.0% 15046 -7.6% 15446
>> -8.3% 15326 reaim.jobs_per_min_child
>> 97.84 -1.1% 96.75 -0.4% 97.43
>> -0.5% 97.37 reaim.jti
>> 72000 -10.8% 64216 -8.3% 66000
>> -8.3% 66000 reaim.max_jobs_per_min
>> 0.36 +10.6% 0.40 +7.8% 0.39
>> +9.4% 0.39 reaim.parent_time
>> 1.58 ± 2% +71.0% 2.70 ± 2% +26.9% 2.01 ± 2%
>> +33.2% 2.11 reaim.std_dev_percent
>> 0.00 ± 5% +110.4% 0.01 ± 3% +48.8% 0.01 ± 7%
>> +65.3% 0.01 ± 3% reaim.std_dev_time
>> 50800 -2.4% 49600 -1.6% 50000
>> -1.8% 49866 reaim.workload
>>
>>
>>
>> --
>> Zhengjun Xing

--
Zhengjun Xing