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

[zhaowenhui (A)]

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@xxxxxxxxxx>
> > Signed-off-by: Zhao Wenhui <zhaowenhui8@xxxxxxxxxx>
> > ---
> >   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