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

[Hao Xu <hao.xu@linux.dev>]

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.

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
-- 
2.25.1