linux-kernel - Re: [PATCH v4 00/11] simplify block layer based on immutable biovecs

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Date:	Sun, 24 May 2015 00:37:32 -0700
From:	Ming Lin <mlin@...nel.org>
To:	Christoph Hellwig <hch@....de>
Cc:	Ming Lin <mlin@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Jens Axboe <axboe@...nel.dk>, Dongsu Park <dpark@...teo.net>
Subject: Re: [PATCH v4 00/11] simplify block layer based on immutable biovecs

On Sat, May 23, 2015 at 7:15 AM, Christoph Hellwig <hch@....de> wrote:
> On Fri, May 22, 2015 at 11:18:32AM -0700, Ming Lin wrote:
>> This will bring not only performance improvements, but also a great amount
>> of reduction in code complexity all over the block layer. Performance gain
>> is possible due to the fact that bio_add_page() does not have to check
>> unnecesary conditions such as queue limits or if biovecs are mergeable.
>> Those will be delegated to the driver level. Kent already said that he
>> actually benchmarked the impact of this with fio on a micron p320h, which
>> showed definitely a positive impact.
>
> We'll need some actual numbers.  I actually like these changes a lot
> and don't even need a performance justification for this fundamentally
> better model, but I'd really prefer to avoid any large scale regressions.
> I don't really expect them, but for code this fundamental we'll just
> need some benchmarks.
>
> Except for that these changes looks good, and the previous version
> passed my tests fine, so with some benchmarks you'ĺl have my ACK.

I'll test it on a 2 sockets server with 10 NVMe drives on Monday.
I'm going to run fio tests:
1. raw NVMe drives direct IO read/write
2. ext4 read/write

Let me know if you have other tests that I can run.
Thanks.

>
> I'd love to see this go into 4.2, but for that we'll need Jens
> approval and a merge into for-next very soon.
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