buffer: Avoid setting buffer bits that are already set

Browse source

It's expensive to set buffer flags that are already set, because that
causes a costly cache line transition.

A common case is setting the "verified" flag during ext4 writes.
This patch checks for the flag being set first.

With the AIM7/creat-clo benchmark testing on a 48G ramdisk based-on ext4
file system, we see 3.3%(15431->15936) improvement of aim7.jobs-per-min on
a 2-sockets broadwell platform.

What the benchmark does is: it forks 3000 processes, and each  process do
the following:
a) open a new file
b) close the file
c) delete the file
until loop=100*1000 times.

The original patch is contributed by Andi Kleen.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Kemi Wang <kemi.wang@intel.com>
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

...

This commit is contained in:

Kemi Wang 2017-10-24 09:16:42 +08:00 • committed by Jens Axboe

parent bea99a5007

commit 60f91826ca

1 changed files with 4 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

5

include/linux/buffer_head.h

View file