[PATCH v5 0/3] fs/file.c: optimize the critical section of file_lock in

[Yu Ma <yu.ma@intel.com>]

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.

v4 -> v5:
Revised patch 3 for some code style issues.

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@suse.cz> and Tim Chen <tim.c.chen@linux.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@suse.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 | 46 ++++++++++++++++++++++++++--------------------
 1 file changed, 26 insertions(+), 20 deletions(-)

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2.43.0