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

[Ming Lin <mlin@kernel.org>]

On Sat, May 23, 2015 at 7:15 AM, Christoph Hellwig <hch@lst.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.