block: convert ThrottleGroup to object with QOM

ThrottleGroup is converted to an object. This will allow the future
throttle block filter drive easy creation and configuration of throttle
groups in QMP and cli.

A new QAPI struct, ThrottleLimits, is introduced to provide a shared
struct for all throttle configuration needs in QMP.

ThrottleGroups can be created via CLI as
    -object throttle-group,id=foo,x-iops-total=100,x-..
where x-* are individual limit properties. Since we can't add non-scalar
properties in -object this interface must be used instead. However,
setting these properties must be disabled after initialization because
certain combinations of limits are forbidden and thus configuration
changes should be done in one transaction. The individual properties
will go away when support for non-scalar values in CLI is implemented
and thus are marked as experimental.

ThrottleGroup also has a `limits` property that uses the ThrottleLimits
struct.  It can be used to create ThrottleGroups or set the
configuration in existing groups as follows:

{ "execute": "object-add",
  "arguments": {
    "qom-type": "throttle-group",
    "id": "foo",
    "props" : {
      "limits": {
          "iops-total": 100
      }
    }
  }
}
{ "execute" : "qom-set",
    "arguments" : {
        "path" : "foo",
        "property" : "limits",
        "value" : {
            "iops-total" : 99
        }
    }
}

This also means a group's configuration can be fetched with qom-get.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 28abb9e6cf..60bd7ec379 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1906,6 +1906,54 @@
             '*iops_size': 'int', '*group': 'str' } }
 
 ##
+# @ThrottleLimits:
+#
+# Limit parameters for throttling.
+# Since some limit combinations are illegal, limits should always be set in one
+# transaction. All fields are optional. When setting limits, if a field is
+# missing the current value is not changed.
+#
+# @iops-total:             limit total I/O operations per second
+# @iops-total-max:         I/O operations burst
+# @iops-total-max-length:  length of the iops-total-max burst period, in seconds
+#                          It must only be set if @iops-total-max is set as well.
+# @iops-read:              limit read operations per second
+# @iops-read-max:          I/O operations read burst
+# @iops-read-max-length:   length of the iops-read-max burst period, in seconds
+#                          It must only be set if @iops-read-max is set as well.
+# @iops-write:             limit write operations per second
+# @iops-write-max:         I/O operations write burst
+# @iops-write-max-length:  length of the iops-write-max burst period, in seconds
+#                          It must only be set if @iops-write-max is set as well.
+# @bps-total:              limit total bytes per second
+# @bps-total-max:          total bytes burst
+# @bps-total-max-length:   length of the bps-total-max burst period, in seconds.
+#                          It must only be set if @bps-total-max is set as well.
+# @bps-read:               limit read bytes per second
+# @bps-read-max:           total bytes read burst
+# @bps-read-max-length:    length of the bps-read-max burst period, in seconds
+#                          It must only be set if @bps-read-max is set as well.
+# @bps-write:              limit write bytes per second
+# @bps-write-max:          total bytes write burst
+# @bps-write-max-length:   length of the bps-write-max burst period, in seconds
+#                          It must only be set if @bps-write-max is set as well.
+# @iops-size:              when limiting by iops max size of an I/O in bytes
+#
+# Since: 2.11
+##
+{ 'struct': 'ThrottleLimits',
+  'data': { '*iops-total' : 'int', '*iops-total-max' : 'int',
+            '*iops-total-max-length' : 'int', '*iops-read' : 'int',
+            '*iops-read-max' : 'int', '*iops-read-max-length' : 'int',
+            '*iops-write' : 'int', '*iops-write-max' : 'int',
+            '*iops-write-max-length' : 'int', '*bps-total' : 'int',
+            '*bps-total-max' : 'int', '*bps-total-max-length' : 'int',
+            '*bps-read' : 'int', '*bps-read-max' : 'int',
+            '*bps-read-max-length' : 'int', '*bps-write' : 'int',
+            '*bps-write-max' : 'int', '*bps-write-max-length' : 'int',
+            '*iops-size' : 'int' } }
+
+##
 # @block-stream:
 #
 # Copy data from a backing file into a block device.