linux-kernel - [PATCH v4 0/3] fs/file.c: optimize the critical section of file

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Message-ID: <20240713023917.3967269-1-yu.ma@intel.com>
Date: Fri, 12 Jul 2024 22:39:14 -0400
From: Yu Ma <yu.ma@...el.com>
To: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	mjguzik@...il.com,
	edumazet@...gle.com
Cc: yu.ma@...el.com,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	pan.deng@...el.com,
	tianyou.li@...el.com,
	tim.c.chen@...el.com,
	tim.c.chen@...ux.intel.com
Subject: [PATCH v4 0/3] fs/file.c: optimize the critical section of file_lock in

pts/blogbench-1.1.0 is a benchmark designed to replicate the
load of a real-world busy file server by multiple threads of
random reads, writes, and rewrites. When running default configuration
with multiple parallel threads, hot spin lock contention is observed
from alloc_fd(), file_closed_fd() and put_unused_fd() around file_lock.

These 3 patches are created to reduce the critical section of file_lock
in alloc_fd() and close_fd(). As a result, on top of patch 1,
pts/blogbench-1.1.0 has been improved by 22% for read and 8% for write
on Intel ICX 160 cores configuration with v6.10-rc7.

v3 -> v4:
1. Rebased the patch set to v6.10-rc7 and updated performance results.
2. Updated patch 1 to revise the order of fd checking.
3. As proposed by Mateusz Guzik <mjguzik gmail.com>, and agreed by Jan Kara
<jack@...e.cz> and Tim Chen <tim.c.chen@...ux.intel.com>, updated patch 3 with
a more generic and scalable fast path for the word contains next_fd.

v2 -> v3:
1. Rebased the patch set to latest v6.10-rc6 and updated the performance results
2. Reordered the patches as suggested by Mateusz Guzik <mjguzik gmail.com>
3. Updated the fast path from alloc_fd() to find_next_fd() as suggested by
Mateusz Guzik <mjguzik gmail.com> and Jan Kara <jack@...e.cz>, it is efficient
and more concise than v2.

v1 -> v2:
1. Rebased the patch set to latest v6.10-rc4 and updated the performance results
2. Fixed the bug identified by Mateusz Guzik in patch 1 with adding rlimit check
for fast path
3. Updated patch 3 to remove sanity_check directly per the alignment with
maintainer

Yu Ma (3):
  fs/file.c: remove sanity_check and add likely/unlikely in alloc_fd()
  fs/file.c: conditionally clear full_fds
  fs/file.c: add fast path in find_next_fd()

 fs/file.c | 50 +++++++++++++++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

-- 
2.43.0