- io_service_time (the actual time in ns taken by the dis to service the IO)
- io_wait_time (the time spent waiting in the IO shceduler queues before
  getting serviced)
- io_serviced (number of IOs serviced from this blkio_group)
- io_service_bytes (Number of bytes served for this cgroup)

These stats are accumulated per operation type helping us to distinguish between
read and write, and sync and async IO. This patch does not increment any of
these stats.

Signed-off-by: Divyesh Shah<dpshah@google.com>
---

 Documentation/cgroups/blkio-controller.txt |   33 +++++
 block/blk-cgroup.c                         |  179 +++++++++++++++++++++++++---
 block/blk-cgroup.h                         |   41 +++++-
 block/cfq-iosched.c                        |    2 
 4 files changed, 229 insertions(+), 26 deletions(-)

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 630879c..ededdca 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -75,6 +75,9 @@ CONFIG_DEBUG_BLK_CGROUP
 
 Details of cgroup files
 =======================
+Writing an int to any of the stats files (which excludes weight) will result
+in all stats for that cgroup to be erased.
+
 - blkio.weight
 	- Specifies per cgroup weight.
 
@@ -92,6 +95,36 @@ 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 ...
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