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

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Message-ID: <5087ebc3-96e9-44a4-a914-eb99f3c33054@kernel.dk>
Date:   Wed, 10 Jul 2019 08:25:38 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        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 7/10/19 8:24 AM, Konstantin Khlebnikov wrote:
> 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.

Huh, oh well. Not a big deal for me, line breaking is easily automated.


-- 
Jens Axboe