Re: [RFC 0/5] support nonblock submission for splice pipe to pipe

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/7/22 09:06, Hao Xu wrote:
> From: Hao Xu <howeyxu@tencent.com>
> 
> splice from pipe to pipe is a trivial case, and we can support nonblock
> try for it easily. splice depends on iowq at all which is slow. Let's
> build a fast submission path for it by supporting nonblock.

fwiw,

https://www.spinics.net/lists/kernel/msg3652757.html



> Wrote a simple test to test time spent of splicing from pipe to pipe:
> 
> 
> Did 50 times test for each, ignore the highest and lowest number,
> calculate the average number:
> 
> before patchset: 119.85 usec
> with patchset: 29.5 usec
> 
> ----------------
> I'm not sure if we should use a io_uring specific flag rather than
> SPLICE_F_NONBLOCK since from mutex_lock_nest to mutex_trylock changes
> the behavior under debug environment I guess. Or maybe there is another
> better option than mutex_trylock?
> 
> 
> Hao Xu (5):
>    io_uring: move sp->len check up for splice and tee
>    pipe: add trylock helpers for pipe lock
>    splice: support nonblock for splice from pipe to pipe
>    io_uring: support nonblock try for splicing from pipe to pipe
>    io_uring: add file_in in io_splice{} to avoid duplicate calculation
> 
>   fs/pipe.c                 | 29 +++++++++++++++++++++
>   fs/splice.c               | 21 +++++++++++++---
>   include/linux/pipe_fs_i.h |  2 ++
>   io_uring/splice.c         | 53 +++++++++++++++++++++++++++++----------
>   4 files changed, 89 insertions(+), 16 deletions(-)
> 
> 
> base-commit: d8271bf021438f468dab3cd84fe5279b5bbcead8

-- 
Pavel Begunkov