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SubjectRe: [PATCH] sched/fair: limit burst to zero when cfs bandwidth is toggled off
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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@huawei.com>
> Signed-off-by: Zhao Wenhui <zhaowenhui8@huawei.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

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