linux-kernel - Re: [PATCH] sched/fair: limit burst to zero when cfs bandwidth is toggled off

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Message-ID: <47efc7e4-75bd-8302-48e8-1ddb2be48886@huawei.com>
Date:   Wed, 23 Nov 2022 16:52:29 +0800
From:   "zhaowenhui (A)" <zhaowenhui8@...wei.com>
To:     <peterz@...radead.org>
CC:     <zhaogongyi@...wei.com>, <dietmar.eggemann@....com>,
        <rostedt@...dmis.org>, <bsegall@...gle.com>, <mgorman@...e.de>,
        <bristot@...hat.com>, <vschneid@...hat.com>,
        <shanpeic@...ux.alibaba.com>, <changhuaixin@...ux.alibaba.com>,
        <tj@...nel.org>, <dtcccc@...ux.alibaba.com>, <mingo@...hat.com>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: limit burst to zero when cfs bandwidth is
 toggled off



在 2022/9/30 16:32, zhaowenhui (A) 写道:
> 
> 
> 在 2022/8/30 11:19, zhaowenhui (A) 写道:
>>
>>
>> 在 2022/8/9 20:03, Zhao Wenhui 写道:
>>> When the quota value in CFS bandwidth is set to -1, that imples the
>>> cfs bandwidth is toggled off. So the burst feature is supposed to
>>> be disable as well.
>>>
>>> Currently, when quota is -1, burst will not be check, so that it can be
>>> set to almost arbitery value. Examples:
>>>          mkdir /sys/fs/cgroup/cpu/test
>>>          echo -1 > /sys/fs/cgroup/cpu/test/cpu.cfs_quota_us
>>>          echo 10000000000000000 > 
>>> /sys/fs/cgroup/cpu/test/cpu.cfs_burst_us
>>>
>>> Moreover, after the burst modified by this way, quota can't be set
>>> to any value:
>>>          echo 100000 > cpu.cfs_quota_us
>>>          -bash: echo: write error: Invalid argument
>>>
>>> This patch can ensure the burst value being zero and unalterable,
>>> when quota is set to -1.
>>>
>>> Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS 
>>> controller")
>>> Reported-by: Zhao Gongyi <zhaogongyi@...wei.com>
>>> Signed-off-by: Zhao Wenhui <zhaowenhui8@...wei.com>
>>> ---
>>>   kernel/sched/core.c | 10 +++++++++-
>>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>>> index ee28253c9ac0..4c1fc01d8c68 100644
>>> --- a/kernel/sched/core.c
>>> +++ b/kernel/sched/core.c
>>> @@ -10584,6 +10584,12 @@ static int tg_set_cfs_bandwidth(struct 
>>> task_group *tg, u64 period, u64 quota,
>>>                        burst + quota > max_cfs_runtime))
>>>           return -EINVAL;
>>> +    /*
>>> +     * Ensure burst equals to zero when quota is -1.
>>> +     */
>>> +    if (quota == RUNTIME_INF && burst)
>>> +        return -EINVAL;
>>> +
>>>       /*
>>>        * Prevent race between setting of cfs_rq->runtime_enabled and
>>>        * unthrottle_offline_cfs_rqs().
>>> @@ -10643,8 +10649,10 @@ static int tg_set_cfs_quota(struct 
>>> task_group *tg, long cfs_quota_us)
>>>       period = ktime_to_ns(tg->cfs_bandwidth.period);
>>>       burst = tg->cfs_bandwidth.burst;
>>> -    if (cfs_quota_us < 0)
>>> +    if (cfs_quota_us < 0) {
>>>           quota = RUNTIME_INF;
>>> +        burst = 0;
>>> +    }
>>>       else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
>>>           quota = (u64)cfs_quota_us * NSEC_PER_USEC;
>>>       else
>>
>> Gentle ping.
>>
>> Thanks,
>> Zhao Wenhui
> 
> Dear Maintainers,
> Hi, this patch has been reviewed by two reviewers over a month ago.
> So, Any more suggestions for this patch or it can be picked?
> 
> Regards,
> Zhao Wenhui

Peter,
Sorry to disturbed, for this patch is submitted long long time ago...
And this is my first patch, so I really wonder if there is something
to be improved for the patch.

Looking forward to your reply.

Thank you,
Zhao Wenhui