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To:     Josef Bacik <josef@toxicpanda.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, dennis@kernel.org
References: <cover.1560510935.git.asml.silence@gmail.com>
 <20190614134037.ie7zs4rb4oyesifr@MacBook-Pro-91.local>
From:   Pavel Begunkov <asml.silence@gmail.com>
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Subject: Re: [PATCH 0/2] Fix misuse of blk_rq_stats in blk-iolatency
Message-ID: <054f3ab6-0a03-ff0e-ac46-5d0fba012cf0@gmail.com>
Date:   Thu, 20 Jun 2019 20:18:55 +0300
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
 linux-kernel@vger.kernel.org, dennis@kernel.org
Message-ID: <054f3ab6-0a03-ff0e-ac46-5d0fba012cf0@gmail.com>
Subject: Re: [PATCH 0/2] Fix misuse of blk_rq_stats in blk-iolatency
References: <cover.1560510935.git.asml.silence@gmail.com>
 <20190614134037.ie7zs4rb4oyesifr@MacBook-Pro-91.local>
In-Reply-To: <20190614134037.ie7zs4rb4oyesifr@MacBook-Pro-91.local>

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Hi,

Josef, thanks for taking a look.


Although, there is nothing critical yet -- just a not working / disabled
optimisation, but changes in stats could sublty break it. E.g. grouping
@batch and @mean into a union will increase estimated average by several
orders of magnitude.

Jens, what do you think?


On 14/06/2019 16:40, Josef Bacik wrote:
> On Fri, Jun 14, 2019 at 02:44:11PM +0300, Pavel Begunkov (Silence) wrot=
e:
>> From: Pavel Begunkov <asml.silence@gmail.com>
>>
>> There are implicit assumptions about struct blk_rq_stats, which make
>> it's very easy to misuse. The first patch fixes consequences, and the
>> second employs type-system to prevent recurrences.
>>
>>
>> Pavel Begunkov (2):
>>   blk-iolatency: Fix zero mean in previous stats
>>   blk-stats: Introduce explicit stat staging buffers
>>
>=20
> I don't have a problem with this, but it's up to Jens I suppose
>=20
> Acked-by: Josef Bacik <josef@toxicpanda.com>
>=20
> Thanks,
>=20
> Josef
>=20

--=20
Yours sincerely,
Pavel Begunkov


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