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

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Message-ID: <b93d70a2-380a-6088-d5ec-8098cfd57033@huawei.com>
Date:   Fri, 30 Sep 2022 16:32:18 +0800
From:   "zhaowenhui (A)" <zhaowenhui8@...wei.com>
To:     <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <linux-kernel@...r.kernel.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>
Subject: Re: [PATCH] sched/fair: limit burst to zero when cfs bandwidth is
 toggled off



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