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

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Message-ID: <20200514145114.GG16815@mtj.duckdns.org>
Date:   Thu, 14 May 2020 10:51:14 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
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 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?

Thanks.

-- 
tejun