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-rw-r--r--Documentation/cgroups/blkio-controller.txt31
1 files changed, 17 insertions, 14 deletions
diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 465351d4cf85..cd45c8ea7463 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -28,16 +28,19 @@ cgroups. Here is what you can do.
- Enable group scheduling in CFQ
CONFIG_CFQ_GROUP_IOSCHED=y
-- Compile and boot into kernel and mount IO controller (blkio).
+- Compile and boot into kernel and mount IO controller (blkio); see
+ cgroups.txt, Why are cgroups needed?.
- mount -t cgroup -o blkio none /cgroup
+ mount -t tmpfs cgroup_root /sys/fs/cgroup
+ mkdir /sys/fs/cgroup/blkio
+ mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
- Create two cgroups
- mkdir -p /cgroup/test1/ /cgroup/test2
+ mkdir -p /sys/fs/cgroup/blkio/test1/ /sys/fs/cgroup/blkio/test2
- Set weights of group test1 and test2
- echo 1000 > /cgroup/test1/blkio.weight
- echo 500 > /cgroup/test2/blkio.weight
+ echo 1000 > /sys/fs/cgroup/blkio/test1/blkio.weight
+ echo 500 > /sys/fs/cgroup/blkio/test2/blkio.weight
- Create two same size files (say 512MB each) on same disk (file1, file2) and
launch two dd threads in different cgroup to read those files.
@@ -46,12 +49,12 @@ cgroups. Here is what you can do.
echo 3 > /proc/sys/vm/drop_caches
dd if=/mnt/sdb/zerofile1 of=/dev/null &
- echo $! > /cgroup/test1/tasks
- cat /cgroup/test1/tasks
+ echo $! > /sys/fs/cgroup/blkio/test1/tasks
+ cat /sys/fs/cgroup/blkio/test1/tasks
dd if=/mnt/sdb/zerofile2 of=/dev/null &
- echo $! > /cgroup/test2/tasks
- cat /cgroup/test2/tasks
+ echo $! > /sys/fs/cgroup/blkio/test2/tasks
+ cat /sys/fs/cgroup/blkio/test2/tasks
- At macro level, first dd should finish first. To get more precise data, keep
on looking at (with the help of script), at blkio.disk_time and
@@ -68,13 +71,13 @@ Throttling/Upper Limit policy
- Enable throttling in block layer
CONFIG_BLK_DEV_THROTTLING=y
-- Mount blkio controller
- mount -t cgroup -o blkio none /cgroup/blkio
+- Mount blkio controller (see cgroups.txt, Why are cgroups needed?)
+ mount -t cgroup -o blkio none /sys/fs/cgroup/blkio
- Specify a bandwidth rate on particular device for root group. The format
for policy is "<major>:<minor> <byes_per_second>".
- echo "8:16 1048576" > /cgroup/blkio/blkio.read_bps_device
+ echo "8:16 1048576" > /sys/fs/cgroup/blkio/blkio.read_bps_device
Above will put a limit of 1MB/second on reads happening for root group
on device having major/minor number 8:16.
@@ -108,7 +111,7 @@ Hierarchical Cgroups
CFQ and throttling will practically treat all groups at same level.
pivot
- / | \ \
+ / / \ \
root test1 test2 test3
Down the line we can implement hierarchical accounting/control support
@@ -149,7 +152,7 @@ Proportional weight policy files
Following is the format.
- #echo dev_maj:dev_minor weight > /path/to/cgroup/blkio.weight_device
+ # echo dev_maj:dev_minor weight > 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