Documentation: Add sysfs ABI change for cfq's target latency.
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/Documentation/ABI/testing/sysfs-cfq-target-latency b/Documentation/ABI/testing/sysfs-cfq-target-latency
new file mode 100644
index 0000000..df0f782
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-cfq-target-latency
@@ -0,0 +1,8 @@
+What: /sys/block/<device>/iosched/target_latency
+Date: March 2012
+contact: Tao Ma <boyu.mt@taobao.com>
+Description:
+ The /sys/block/<device>/iosched/target_latency only exists
+ when the user sets cfq to /sys/block/<device>/scheduler.
+ It contains an estimated latency time for the cfq. cfq will
+ use it to calculate the time slice used for every task.