Re: [PATCH v2] block: optimise bvec_iter_advance()

[Jens Axboe]

On 11/30/19 1:23 PM, Pavel Begunkov wrote:
> bvec_iter_advance() is quite popular, but compilers fail to do proper
> alias analysis and optimise it good enough. The assembly is checked
> for gcc 9.2, x86-64.
>
> - remove @iter->bi_size from min(...), as it's always less than @bytes.
> Modify at the beginning and forget about it.
>
> - the compiler isn't able to collapse memory dependencies and remove
> writes in the loop. Help it by explicitely using local vars.

Applied, thanks.

--
Jens Axboe