io-controller: Document for blkio.weight_device
Here is the document for blkio.weight_device
Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index db054ea..d422b41 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -76,9 +76,38 @@
Details of cgroup files
=======================
- blkio.weight
- - Specifies per cgroup weight.
+ - Specifies per cgroup weight. This is default weight of the group
+ on all the devices until and unless overridden by per device rule.
+ (See blkio.weight_device).
Currently allowed range of weights is from 100 to 1000.
+- blkio.weight_device
+ - One can specify per cgroup per device rules using this interface.
+ These rules override the default value of group weight as specified
+ by blkio.weight.
+
+ Following is the format.
+
+ #echo dev_maj:dev_minor weight > /path/to/cgroup/blkio.weight_device
+ Configure weight=300 on /dev/sdb (8:16) in this cgroup
+ # echo 8:16 300 > blkio.weight_device
+ # cat blkio.weight_device
+ dev weight
+ 8:16 300
+
+ Configure weight=500 on /dev/sda (8:0) in this cgroup
+ # echo 8:0 500 > blkio.weight_device
+ # cat blkio.weight_device
+ dev weight
+ 8:0 500
+ 8:16 300
+
+ Remove specific weight for /dev/sda in this cgroup
+ # echo 8:0 0 > blkio.weight_device
+ # cat blkio.weight_device
+ dev weight
+ 8:16 300
+
- blkio.time
- disk time allocated to cgroup per device in milliseconds. First
two fields specify the major and minor number of the device and