throttle: Add throttle group support
The throttle group support use a cooperative round robin scheduling
algorithm.
The principles of the algorithm are simple:
- Each BDS of the group is used as a token in a circular way.
- The active BDS computes if a wait must be done and arms the right
timer.
- If a wait must be done the token timer will be armed so the token
will become the next active BDS.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: f0082a86f3ac01c46170f7eafe2101a92e8fde39.1433779731.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 8411d4f..3087154 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1062,6 +1062,27 @@
#
# Change I/O throttle limits for a block drive.
#
+# Since QEMU 2.4, each device with I/O limits is member of a throttle
+# group.
+#
+# If two or more devices are members of the same group, the limits
+# will apply to the combined I/O of the whole group in a round-robin
+# fashion. Therefore, setting new I/O limits to a device will affect
+# the whole group.
+#
+# The name of the group can be specified using the 'group' parameter.
+# If the parameter is unset, it is assumed to be the current group of
+# that device. If it's not in any group yet, the name of the device
+# will be used as the name for its group.
+#
+# The 'group' parameter can also be used to move a device to a
+# different group. In this case the limits specified in the parameters
+# will be applied to the new group only.
+#
+# I/O limits can be disabled by setting all of them to 0. In this case
+# the device will be removed from its group and the rest of its
+# members will no be affected. The 'group' parameter is ignored.
+#
# @device: The name of the device
#
# @bps: total throughput limit in bytes per second
@@ -1090,6 +1111,8 @@
#
# @iops_size: #optional an I/O size in bytes (Since 1.7)
#
+# @group: #optional throttle group name (Since 2.4)
+#
# Returns: Nothing on success
# If @device is not a valid block device, DeviceNotFound
#
@@ -1101,7 +1124,7 @@
'*bps_max': 'int', '*bps_rd_max': 'int',
'*bps_wr_max': 'int', '*iops_max': 'int',
'*iops_rd_max': 'int', '*iops_wr_max': 'int',
- '*iops_size': 'int' } }
+ '*iops_size': 'int', '*group': 'str' } }
##
# @block-stream:
