[PATCH] block: doc: add slice_idle_us to bfq documentation

[John Pittman <jpittman@redhat.com>]

Of the tunables available for the bfq I/O scheduler,
the only one missing from the documentation in
'Documentation/block/bfq-iosched.txt' is slice_idle_us.
Add this tunable to the documentation and a short
explanation of its purpose.

Signed-off-by: John Pittman <jpittman@redhat.com>
---
 Documentation/block/bfq-iosched.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt
index 8d8d8f06cab2..98a8dd5ee385 100644
--- a/Documentation/block/bfq-iosched.txt
+++ b/Documentation/block/bfq-iosched.txt
@@ -357,6 +357,13 @@ video playing/streaming, a very low drop rate may be more important
 than maximum throughput. In these cases, consider setting the
 strict_guarantees parameter.
 
+slice_idle_us
+-------------
+
+Controls the same tuning parameter as slice_idle, but in microseconds.
+Either tunable can be used to set idling behavior.  Afterwards, the
+other tunable will reflect the newly set value in sysfs.
+
 strict_guarantees
 -----------------
 
-- 
2.17.2