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

Xing Zhengjun
2020-06-16T03:24:13Z

On 6/15/2020 11:10 PM, Hillf Danton wrote:
>
> On Mon, 15 Jun 2020 10:10:41 +0200 Vincent Guittot wrote:
>> Le lundi 15 juin 2020 15:26:59 (+0800), Xing Zhengjun a crit :
>>>
>>> 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 regression still existed.
>>
>> Thanks for the test.
>
> Thanks.
>
>> 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;
>>
>>
>>>
>>> =========================================================================================
>>> 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
>>>
>
> Following the introduction of runnable_avg there came a gap between it
> and util, and it can be supposedly filled up by determining the pivot
> point using the imb percent. The upside is that no heuristic is added.
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8215,15 +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))
> - return true;
> -
> - return false;
> + return sgs->group_capacity * imbalance_pct >
> + (sgs->group_util + sgs->group_runnable) *50;
> }
>
> /*
> @@ -8240,15 +8233,8 @@ 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))
> - return true;
> -
> - return false;
> + return sgs->group_capacity * imbalance_pct <
> + (sgs->group_util + sgs->group_runnable) *50;
> }
>
> /*
>

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
1d5ee1e6dab1f8903cd7219fbcc5ac2f728ac80c (the test patch)

9f68395333ad7f5b 070f5e860ee2bf588c99ef7b4c2 v5.7
1d5ee1e6dab1f8903cd7219fbcc
---------------- --------------------------- ---------------------------
---------------------------
%stddev %change %stddev %change
%stddev %change %stddev
\ | \ | \
| \
0.69 -10.3% 0.62 -9.1% 0.62
-6.8% 0.64 reaim.child_systime
0.62 -1.0% 0.61 +0.5% 0.62
+0.6% 0.62 reaim.child_utime
66870 -10.0% 60187 -7.6% 61787
-5.7% 63058 reaim.jobs_per_min
16717 -10.0% 15046 -7.6% 15446
-5.7% 15764 reaim.jobs_per_min_child
97.84 -1.1% 96.75 -0.4% 97.43
-0.5% 97.31 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
+6.0% 0.38 reaim.parent_time
1.58 ± 2% +71.0% 2.70 ± 2% +26.9% 2.01 ±
2% +33.1% 2.10 ± 3% reaim.std_dev_percent
0.00 ± 5% +110.4% 0.01 ± 3% +48.8% 0.01 ±
7% +58.1% 0.01 ± 6% reaim.std_dev_time
50800 -2.4% 49600 -1.6% 50000
-0.8% 50400 reaim.workload

--
Zhengjun Xing