Documentation: fix cgroup typos and formatting

[firefly-linux-kernel-4.4.55.git] / Documentation / cgroups / blkio-controller.txt

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 4ed7b5ceeed212c1b7a734451456896f4759ee9d..cd45c8ea7463f71eccee9d82ce6a82b47bcee467 100644 (file)
--- 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
@@ -140,7 +143,7 @@ Proportional weight policy files
        - 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.
+         Currently allowed range of weights is from 10 to 1000.
 
 - blkio.weight_device
        - One can specify per cgroup per device rules using this interface.
@@ -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
@@ -343,34 +346,6 @@ Common files among various policies
 
 CFQ sysfs tunable
 =================
-/sys/block/<disk>/queue/iosched/group_isolation
------------------------------------------------
-
-If group_isolation=1, it provides stronger isolation between groups at the
-expense of throughput. By default group_isolation is 0. In general that
-means that if group_isolation=0, expect fairness for sequential workload
-only. Set group_isolation=1 to see fairness for random IO workload also.
-
-Generally CFQ will put random seeky workload in sync-noidle category. CFQ
-will disable idling on these queues and it does a collective idling on group
-of such queues. Generally these are slow moving queues and if there is a
-sync-noidle service tree in each group, that group gets exclusive access to
-disk for certain period. That means it will bring the throughput down if
-group does not have enough IO to drive deeper queue depths and utilize disk
-capacity to the fullest in the slice allocated to it. But the flip side is
-that even a random reader should get better latencies and overall throughput
-if there are lots of sequential readers/sync-idle workload running in the
-system.
-
-If group_isolation=0, then CFQ automatically moves all the random seeky queues
-in the root group. That means there will be no service differentiation for
-that kind of workload. This leads to better throughput as we do collective
-idling on root sync-noidle tree.
-
-By default one should run with group_isolation=0. If that is not sufficient
-and one wants stronger isolation between groups, then set group_isolation=1
-but this will come at cost of reduced throughput.
-
 /sys/block/<disk>/queue/iosched/slice_idle
 ------------------------------------------
 On a faster hardware CFQ can be slow, especially with sequential workload.