Message-ID: <5456B4F8.1000608@nod.at>
Date: Sun, 02 Nov 2014 23:49:28 +0100
From: Richard Weinberger <richard@nod.at>
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To: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>, hch@infradead.org,
        axboe@fb.com, dedekind1@gmail.com
CC: dwmw2@infradead.org, computersforpeace@gmail.com,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] UBI: Block: Add blk-mq support
References: <1414933255-3795-1-git-send-email-richard@nod.at> <5456A787.5060104@free-electrons.com> <5456AE72.1010409@nod.at> <5456AFEA.6000507@free-electrons.com>
In-Reply-To: <5456AFEA.6000507@free-electrons.com>
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Am 02.11.2014 um 23:27 schrieb Ezequiel Garcia:
> Wow. Where did you run this and on top of what storage device?

nandsim, to make sure that the MTD is not our bottleneck.

> I'm still interested in the memory footprint, UBI is already heavy enou=
gh.

AFAICT blk-mq allocates one struct ubiblock_pdu per device.
As all IO is done via scattergather the memory footprint should be good.
But I'm sure Christoph can tell you the glory details.

>>> I kind of like the negative diffstat, but the code doesn't look clean=
er
>>> or simpler.
>>>
>>> In other words, we need a good reason before we agree on making this
>>> "zen style" driver more complex.
>>
>> After reading my patch again I think we could move ubiblock_read_to_sg=
()
>> to kapi.c or io.c. It is rather generic and maybe we can tun more UBI =
users to
>> scattergather such that less vmalloc()s are needed.
>>
>> This would also make the diffstat nicer...
>>
>=20
> Yes, any additional effort to make the current patch any simpler would
> be great. In its current form it seems rather cumbersome to me.

Why cumbersome? It changes the way the driver works as blk-mq works diffe=
rently.
If you look at other blk-mq conversion patches you'll notice that they al=
l change
a lot.

> If you can re-submit something better and put a more verbose commit log=
,
> I'd really appreciate it :)

First I wait for a review. I'm not sure whether I'm used blk-ml correctly=
=2E

Thanks,
//richard


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