linux-kernel - Re: [PATCH] blk-throttle: fix zero wait time for iops throttled group

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Message-ID: <f4be51ff-e426-cc44-db94-3c26e2cfbca9@yandex-team.ru>
Date:   Wed, 10 Jul 2019 17:24:16 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Liu Bo <bo.liu@...ux.alibaba.com>, stable@...r.kernel.org
Subject: Re: [PATCH] blk-throttle: fix zero wait time for iops throttled group

On 10.07.2019 17:00, Jens Axboe wrote:
> On 7/8/19 9:29 AM, Konstantin Khlebnikov wrote:
>> After commit 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops
>> limit is enforced") wait time could be zero even if group is throttled and
>> cannot issue requests right now. As a result throtl_select_dispatch() turns
>> into busy-loop under irq-safe queue spinlock.
>>
>> Fix is simple: always round up target time to the next throttle slice.
> 
> Applied, thanks. In the future, please break lines at 72 chars in
> commit messages, I fixed it up.
> 

Ok, but Documentation/process/submitting-patches.rst and
scripts/checkpatch.pl recommends 75 chars per line.