linux-kernel - Re: [PATCH 5.11] block: optimise for_each

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Message-ID: <0b40b474-1aaa-cdaf-567d-572bcb285aa7@gmail.com>
Date:   Tue, 24 Nov 2020 13:00:01 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        ming.lei@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.11] block: optimise for_each_bvec() advance

On 24/11/2020 11:22, Christoph Hellwig wrote:
> On Tue, Nov 24, 2020 at 10:21:23AM +0000, Pavel Begunkov wrote:
>> Because of how for_each_bvec() works it never advances across multiple
>> entries at a time, so bvec_iter_advance() is an overkill. Add
>> specialised bvec_iter_advance_single() that is faster. It also handles
>> zero-len bvecs, so can kill bvec_iter_skip_zero_bvec().
> 
> bvec_iter_advance_single needs a comment describing how it can be

agree

> used.  Also can you take a look at the other callers and see who
> can be switched over?  If you are not sure ask the relevant maintainers. 

There are bio_advanced*(), that are used all across block layer.
Considering that all that is inlined it's going to be a good win.

I'll resend it as a part of a series converting some users.
For others like net, I'd rather wait until it lands.

-- 
Pavel Begunkov