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 (file)
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.