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author | Dave Hansen <dave.hansen@linux.intel.com> | 2015-09-05 01:43:01 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-09-05 02:54:41 +0300 |
commit | 7c49b8616460ebb12ee56d80d1abfbc20b6f3cbb (patch) | |
tree | 2653f9506f7866172151231f57d4f3cfe0fdc945 /fs/notify/fdinfo.c | |
parent | 031e29b5877f31676739dc2f847d04c2c0732034 (diff) | |
download | linux-7c49b8616460ebb12ee56d80d1abfbc20b6f3cbb.tar.xz |
fs/notify: optimize inotify/fsnotify code for unwatched files
I have a _tiny_ microbenchmark that sits in a loop and writes single
bytes to a file. Writing one byte to a tmpfs file is around 2x slower
than reading one byte from a file, which is a _bit_ more than I expecte.
This is a dumb benchmark, but I think it's hard to deny that write() is
a hot path and we should avoid unnecessary overhead there.
I did a 'perf record' of 30-second samples of read and write. The top
item in a diffprofile is srcu_read_lock() from fsnotify(). There are
active inotify fd's from systemd, but nothing is actually listening to
the file or its part of the filesystem.
I *think* we can avoid taking the srcu_read_lock() for the common case
where there are no actual marks on the file. This means that there will
both be nothing to notify for *and* implies that there is no need for
clearing the ignore mask.
This patch gave a 13.1% speedup in writes/second on my test, which is an
improvement from the 10.8% that I saw with the last version.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Paris <eparis@redhat.com>
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Robert Love <rlove@rlove.org>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/notify/fdinfo.c')
0 files changed, 0 insertions, 0 deletions