blkio: Core implementation of throttle policy

o Actual implementation of throttling policy in block layer. Currently it
  implements READ and WRITE bytes per second throttling logic. IOPS throttling
  comes in later patches.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 2de5b1cbadd9..950ba26f7233 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -634,11 +634,14 @@ config BLK_CGROUP
 
         Currently, CFQ IO scheduler uses it to recognize task groups and
         control disk bandwidth allocation (proportional time slice allocation)
-        to such task groups.
+        to such task groups. It is also used by bio throttling logic in
+        block layer to implement upper limit in IO rates on a device.
 
         This option only enables generic Block IO controller infrastructure.
-        One needs to also enable actual IO controlling logic in CFQ for it
-        to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
+        One needs to also enable actual IO controlling logic/policy. For
+        enabling proportional weight division of disk bandwidth in CFQ seti
+        CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
+        CONFIG_BLK_THROTTLE=y.
 
         See Documentation/cgroups/blkio-controller.txt for more information.