linux-kernel - Re: [PATCH V4 03/15] blk-throttle: configure bps/iops limit for cgroup in high limit

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Date:   Tue, 22 Nov 2016 15:11:21 -0800
From:   Shaohua Li <shli@...com>
To:     Tejun Heo <tj@...nel.org>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <Kernel-team@...com>, <axboe@...com>, <vgoyal@...hat.com>
Subject: Re: [PATCH V4 03/15] blk-throttle: configure bps/iops limit for
 cgroup in high limit

On Tue, Nov 22, 2016 at 03:16:43PM -0500, Tejun Heo wrote:
> On Mon, Nov 14, 2016 at 02:22:10PM -0800, Shaohua Li wrote:
> > each queue will have a state machine. Initially queue is in LIMIT_HIGH
> > state, which means all cgroups will be throttled according to their high
> > limit. After all cgroups with high limit cross the limit, the queue state
> > gets upgraded to LIMIT_MAX state.
> > cgroups without high limit will use max limit for their high limit.
> 
> Haven't looked at the actual mechanism yet so please correct me if I'm
> getting it wrong but at least the above explanation reads incorrect.
> Shouldn't max limits applied regardless of whether other cgroups are
> above high or not?

That's true. Since the max limit is higher than high limit (the interface patch
2 has the check), if cgroup is throttled according to high limit, max limit is
respected too.

Thanks,
Shaohua