From mboxrd@z Thu Jan  1 00:00:00 1970
From: Richard Palethorpe <rpalethorpe@suse.de>
Date: Tue, 01 Jun 2021 11:42:48 +0100
Subject: [LTP] [PATCH v2 6/6] sched/cgroup: Add cfs_bandwidth01
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Hello Li,

Li Wang <liwang@redhat.com> writes:

>> > > [root@dhcp-66-83-181 cfs-scheduler]# ./cfs_bandwidth01
>> > > tst_test.c:1313: TINFO: Timeout per run is 0h 05m 00s
>> > > tst_buffers.c:55: TINFO: Test is using guarded buffers
>> > > cfs_bandwidth01.c:48: TINFO: Set 'worker1/cpu.max' = '3000 10000'
>> > > cfs_bandwidth01.c:48: TINFO: Set 'worker2/cpu.max' = '2000 10000'
>> > > cfs_bandwidth01.c:48: TINFO: Set 'worker3/cpu.max' = '3000 10000'
>> > > cfs_bandwidth01.c:111: TPASS: Scheduled bandwidth constrained workers
>> > > cfs_bandwidth01.c:42: TBROK:
>> > > vdprintf(10</sys/fs/cgroup/cpu,cpuacct/ltp/test-8450/level2>,
>> > > 'cpu.cfs_quota_us', '%u'<5000>): EINVAL (22)
>> >
>> > I wonder if your kernel disallows setting this on a trunk node after it
>> > has been set on leaf nodes (with or without procs in)?
>>
>> After looking a while, I think the CGrup V1 disallows the parent quota
>> less than the max value of its children.
>>
>> This means we should set in level2 at least '3000/10000', just like what
>> we did for level3.
>>
>>   cfs_bandwidth01.c:48: TINFO: Set 'worker1/cpu.max' = '3000 10000'
>>   cfs_bandwidth01.c:48: TINFO: Set 'worker2/cpu.max' = '2000 10000'
>>   cfs_bandwidth01.c:48: TINFO: Set 'worker3/cpu.max' = '3000 10000'
>>
>> But in the failure, it shows level2 only set to 5000/100000 (far less than
>> 3000/10000), that's because function set_cpu_quota changes the system
>> default value 'cpu.cfs_period_us' from 100000 to 10000.
>
> Or, just reverse the code order to set cfs_period_us first, that also works.
>
> --- a/testcases/kernel/sched/cfs-scheduler/cfs_bandwidth01.c
> +++ b/testcases/kernel/sched/cfs-scheduler/cfs_bandwidth01.c
> @@ -38,10 +38,10 @@ static void set_cpu_quota(const struct
> tst_cgroup_group *const cg,
>                 SAFE_CGROUP_PRINTF(cg, "cpu.max",
>                                    "%u %u", quota_us, period_us);
>         } else {
> -               SAFE_CGROUP_PRINTF(cg, "cpu.max",
> -                                  "%u", quota_us);
>                 SAFE_CGROUP_PRINTF(cg, "cpu.cfs_period_us",
>                                   "%u", period_us);
> +               SAFE_CGROUP_PRINTF(cg, "cpu.max",
> +                                  "%u", quota_us);
>         }

Thanks, that is a nice fix.


-- 
Thank you,
Richard.