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

[zhaowenhui (A)]

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@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

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