linux-kernel - Re: [PATCH block/for-linus] iocost: don't let vrate run wild while there's no saturation signal

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Date:   Thu, 14 May 2020 09:34:17 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Tejun Heo <tj@...nel.org>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, newella@...com
Subject: Re: [PATCH block/for-linus] iocost: don't let vrate run wild while
 there's no saturation signal

On 5/14/20 8:51 AM, Tejun Heo wrote:
> On Mon, Oct 14, 2019 at 05:18:11PM -0700, Tejun Heo wrote:
>> When the QoS targets are met and nothing is being throttled, there's
>> no way to tell how saturated the underlying device is - it could be
>> almost entirely idle, at the cusp of saturation or anywhere inbetween.
>> Given that there's no information, it's best to keep vrate as-is in
>> this state.  Before 7cd806a9a953 ("iocost: improve nr_lagging
>> handling"), this was the case - if the device isn't missing QoS
>> targets and nothing is being throttled, busy_level was reset to zero.
> ...
>> Signed-off-by: Tejun Heo <tj@...nel.org>
>> Reported-by: Andy Newell <newella@...com>
>> Fixes: 7cd806a9a953 ("iocost: improve nr_lagging handling")
> 
> Jens, this one fell through the cracks. It still applies with only a small
> offset. Can you please apply?

Looks like it did, queued up for 5.8 now.

-- 
Jens Axboe