Experimental change for btrfs perf

BUG=None
TEST=None

Change-Id: I0568e685855b404a11dcbb39f786bc776b32ca0a
Reviewed-on: https://chromium-review.googlesource.com/467766
Commit-Ready: Xiaochu Liu <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
3 files changed