Re: [Qemu-devel] [PATCH v4 6/6] trace: Add QAPI/QMP interfaces to query and control per-vCPU tracing state

[Lluís Vilanova]

Markus Armbruster writes:

> Lluís Vilanova <address@hidden> writes:
>> Markus Armbruster writes:
>> 
>>> Lluís Vilanova <address@hidden> writes:
[...]
>>>> diff --git a/qapi/trace.json b/qapi/trace.json
>>>> index 01b0a52..25d8095 100644
>>>> --- a/qapi/trace.json
>>>> +++ b/qapi/trace.json
>>>> @@ -1,6 +1,6 @@
>>>> # -*- mode: python -*-
>>>> #
>>>> -# Copyright (C) 2011-2014 Lluís Vilanova <address@hidden>
>>>> +# Copyright (C) 2011-2016 Lluís Vilanova <address@hidden>
>>>> #
>>>> # This work is licensed under the terms of the GNU GPL, version 2 or later.
>>>> # See the COPYING file in the top-level directory.
>>>> @@ -29,11 +29,12 @@
>>>> #
>>>> # @name: Event name.
>>>> # @state: Tracing state.
>>>> +# @vcpu: Whether this is a per-vCPU event (since 2.7).
>>>> #
>>>> # Since 2.2
>>>> ##
>>>> { 'struct': 'TraceEventInfo',
>>>> -  'data': {'name': 'str', 'state': 'TraceEventState'} }
>>>> +  'data': {'name': 'str', 'state': 'TraceEventState', 'vcpu': 'bool'} }
>>>> 
>>>> ##
>>>> # @trace-event-get-state:
>>>> @@ -41,13 +42,18 @@
>>>> # Query the state of events.
>>>> #
>>>> # @name: Event name pattern (case-sensitive glob).
>>>> +# @vcpu: #optional The vCPU to check (any by default; since 2.7).
>>>> #
>>>> # Returns: a list of @TraceEventInfo for the matching events
>>>> #
>>>> +# For any event without the "vcpu" property:
>> 
>>> All events have the vcpu property, but for some of them the property's
>>> value is false.
>> 
>> Hmmm, do you mean in the generated event array? Here, I was referring to 
>> wether
>> an event has the "vcpu" property in "trace-events". I can clarify that.

> What is "trace-events"?  The file in the source tree?

Exactly. Adding the "tcgv" property to an event on that file is what defines
whether the event is per-vCPU.


[...]
>>>> +# - If @name is not a pattern and @vcpu is set, an error is raised.
>> 
>>> Perhaps we could clarify as follows:
>> 
>>> # Returns: a list of @TraceEventInfo for the matching events
>>> #
>>> # An event matches if
>>> # - its name matches the @name pattern, and
>>> # - if @vcpu is given, its vCPU equals @vcpu.
>>> # It follows that with @vcpu given, the query can match only per-vCPU
>>> # events.  Special case: if the name is an exact match, you get an error
>>> # instead of an empty list.
>> 
>> Doesn't sound entirely right to me:
>> 
>> # Returns: a list of @TraceEventInfo for the matching events
>> #
>> # An event matches if
>> # - its name matches the @name pattern, and
>> # - if @vcpu is given, the event is a per-vCPU one (has the "vcpu" property 
>> in
>> #   "trace-events").

> Fails to mention that @vcpu selects the TraceEventInfo for that
> particular VCPU.  That's what I tried to express by "its vCPU equals
> @vcpu".
[...]

Right.


Thanks,
  Lluis