linux-kernel - Re: [PATCH V5 04/17] blk-throttle: configure bps/iops limit for cgroup in low limit

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Message-ID: <20170109173518.GF12827@mtj.duckdns.org>
Date:   Mon, 9 Jan 2017 12:35:18 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Shaohua Li <shli@...com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, axboe@...com, vgoyal@...hat.com
Subject: Re: [PATCH V5 04/17] blk-throttle: configure bps/iops limit for
 cgroup in low limit

Hello,

On Thu, Dec 15, 2016 at 12:32:55PM -0800, Shaohua Li wrote:
> each queue will have a state machine. Initially queue is in LIMIT_LOW
> state, which means all cgroups will be throttled according to their low
> limit. After all cgroups with low limit cross the limit, the queue state
> gets upgraded to LIMIT_MAX state.

As with the previous patch, I don't think it's correct to default to
MAX for LIMIT_LOW and then enforce it.  Without specific
configuration, a cgroup should always be above below (so, no latency
requirement) and below max (no hard limiting).

Thanks.

-- 
tejun