Re: [Qemu-devel] [PATCH 02/11] Add migrate-set-capabilities and query-migrate-capabilities

[Eric Blake]

On 08/06/2012 10:04 AM, Orit Wasserman wrote:
> On 08/06/2012 05:26 PM, Eric Blake wrote:
>> On 08/05/2012 03:13 AM, Orit Wasserman wrote:
>>> The management can enable/disable a capability for the next migration by 
>>> using
>>> migrate-set-apabilities QMP command.
>>
>> s/set-apabilities/set-capabilities/
>>

>> In HMP, are migrate_supported_capabilities and migrate_capabilities
>> redundant?  That is, I think I can use either command to answer both
>> questions "what capabilities exist" and "what is the current state of
>> all capabilities that exist", since _both_ commands output a list of
>> capability names as well as an on/off designator.  If my analysis is
>> right, then we don't need migrate_supported_capabilities.
> No 'info migrate_supported_capabilities' shows the capabilities this version 
> of QEMU can supports.
> and 'info migrate_capabilities' show what are the state of capabilities for 
> the migration, i.e what is enabled.

Let's compare:

patch 1/11:

+void hmp_info_migrate_supported_capabilities(Monitor *mon)
+{
+    MigrationCapabilityStatusList *caps_list, *cap;
+
+    caps_list = qmp_query_migrate_supported_capabilities(NULL);
+    if (!caps_list) {
+        monitor_printf(mon, "No supported migration capabilities found\n");
+        return;
+    }
+
+    for (cap = caps_list; cap; cap = cap->next) {
+        monitor_printf(mon, "%s: %s ",
+                       MigrationCapability_lookup[cap->value->capability],
+                       cap->value->state ? "on" : "off");


patch 2/11:

+void hmp_info_migrate_capabilities(Monitor *mon)
+{
+    MigrationCapabilityStatusList *caps, *cap;
+
+    caps = qmp_query_migrate_capabilities(NULL);
+
+    if (caps) {
+        monitor_printf(mon, "capabilities: ");
+        for (cap = caps; cap; cap = cap->next) {
+            monitor_printf(mon, "%s: %s ",
+
MigrationCapability_lookup[cap->value->capability],
+                           cap->value->state ? "on" : "off");

That is, BOTH commands end up iterating over a list of caps, and output
identical information in the case where caps exist of 'name: state' for
each capability.

They really ARE redundant - both commands are telling me:

capabilities:
xbzrle: on
foobar: off

which I can read to answer both my question of 'what is supported'
(xbzrle and foobar) and 'what is enabled' (xbzrle).  I see no need to
have to commands to tell me the same information, so I'd prefer the
shorter name.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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