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Subject: Re: [PATCH] blk-throttle: fix zero wait time for iops throttled group
To:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Liu Bo <bo.liu@linux.alibaba.com>, stable@vger.kernel.org
References: <156259979778.2486.6296077059654653057.stgit@buzz>
 <30caacb5-4d45-016b-a97d-db8b37010218@kernel.dk>
From:   Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Message-ID: <f4be51ff-e426-cc44-db94-3c26e2cfbca9@yandex-team.ru>
Date:   Wed, 10 Jul 2019 17:24:16 +0300
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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.