blkio: Changes to IO controller additional stats patches

[linux-beck.git] / Documentation / cgroups / blkio-controller.txt

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 630879cd9a42693cbf2ac9748a6a2b80182d0612..ed04fe9cce1a2abeea2e302b2f52dee38694be76 100644 (file)
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -77,7 +77,6 @@ Details of cgroup files
 =======================
 - blkio.weight
        - Specifies per cgroup weight.
-
          Currently allowed range of weights is from 100 to 1000.
 
 - blkio.time
@@ -92,6 +91,49 @@ Details of cgroup files
          third field specifies the number of sectors transferred by the
          group to/from the device.
 
+- blkio.io_service_bytes
+       - Number of bytes transferred to/from the disk by the group. These
+         are further divided by the type of operation - read or write, sync
+         or async. First two fields specify the major and minor number of the
+         device, third field specifies the operation type and the fourth field
+         specifies the number of bytes.
+
+- blkio.io_serviced
+       - Number of IOs completed to/from the disk by the group. These
+         are further divided by the type of operation - read or write, sync
+         or async. First two fields specify the major and minor number of the
+         device, third field specifies the operation type and the fourth field
+         specifies the number of IOs.
+
+- blkio.io_service_time
+       - Total amount of time between request dispatch and request completion
+         for the IOs done by this cgroup. This is in nanoseconds to make it
+         meaningful for flash devices too. For devices with queue depth of 1,
+         this time represents the actual service time. When queue_depth > 1,
+         that is no longer true as requests may be served out of order. This
+         may cause the service time for a given IO to include the service time
+         of multiple IOs when served out of order which may result in total
+         io_service_time > actual time elapsed. This time is further divided by
+         the type of operation - read or write, sync or async. First two fields
+         specify the major and minor number of the device, third field
+         specifies the operation type and the fourth field specifies the
+         io_service_time in ns.
+
+- blkio.io_wait_time
+       - Total amount of time the IOs for this cgroup spent waiting in the
+         scheduler queues for service. This can be greater than the total time
+         elapsed since it is cumulative io_wait_time for all IOs. It is not a
+         measure of total time the cgroup spent waiting but rather a measure of
+         the wait_time for its individual IOs. For devices with queue_depth > 1
+         this metric does not include the time spent waiting for service once
+         the IO is dispatched to the device but till it actually gets serviced
+         (there might be a time lag here due to re-ordering of requests by the
+         device). This is in nanoseconds to make it meaningful for flash
+         devices too. This time is further divided by the type of operation -
+         read or write, sync or async. First two fields specify the major and
+         minor number of the device, third field specifies the operation type
+         and the fourth field specifies the io_wait_time in ns.
+
 - blkio.dequeue
        - Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
          gives the statistics about how many a times a group was dequeued
@@ -99,6 +141,10 @@ Details of cgroup files
          and minor number of the device and third field specifies the number
          of times a group was dequeued from a particular device.
 
+- blkio.reset_stats
+       - Writing an int to this file will result in resetting all the stats
+         for that cgroup.
+
 CFQ sysfs tunable
 =================
 /sys/block/<disk>/queue/iosched/group_isolation