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Re: [Qemu-devel] [PATCH v3 13/18] trace: dynamically allocate event IDs
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH v3 13/18] trace: dynamically allocate event IDs at runtime |
Date: |
Tue, 20 Sep 2016 14:50:03 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Mon, Sep 19, 2016 at 08:05:12PM +0200, Lluís Vilanova wrote:
> Daniel P Berrange writes:
>
> > Instead of having the code generator assign event IDs and
> > event VCPU IDs, assign them when the events are registered
> > at runtime. This will allow us allow code to be generated
> > from individual trace-events without having to figure out
> > globally unique numbering at build time.
>
> > Signed-off-by: Daniel P. Berrange <address@hidden>
> > ---
> > scripts/tracetool/format/events_c.py | 10 ++--------
> > scripts/tracetool/format/events_h.py | 7 -------
> > trace/control.c | 11 ++++++++++-
> > 3 files changed, 12 insertions(+), 16 deletions(-)
>
> > diff --git a/scripts/tracetool/format/events_c.py
> > b/scripts/tracetool/format/events_c.py
> > index 7f00b50..1b5790d 100644
> > --- a/scripts/tracetool/format/events_c.py
> > +++ b/scripts/tracetool/format/events_c.py
> > @@ -28,25 +28,19 @@ def generate(events, backend):
> > for e in events:
> > out('uint16_t %s;' % e.api(e.QEMU_DSTATE))
>
> > - next_id = 0
> > - next_vcpu_id = 0
> > for e in events:
> > - id = next_id
> > - next_id += 1
> > if "vcpu" in e.properties:
> > - vcpu_id = next_vcpu_id
> > - next_vcpu_id += 1
> > + vcpu_id = 0
> > else:
> > vcpu_id = "TRACE_VCPU_EVENT_NONE"
> > out('TraceEvent %(event)s = {',
> > - ' .id = %(id)s,',
> > + ' .id = 0,',
>
> Better to use some invalid value, like in TRACE_VCPU_EVENT_NONE.
I don't think it adds anything todo that - TRACE_VCPU_EVENT_NONE is
special because it is a persistent value for lifetime of QEMU
that will be used by runtime comparisons. In contrast this is
just a placeholder that gets replaced by the real value immediately
at startup in trace_event_register_group(). We never even check
the statically set value of 'id' - we just unconditionally replace
it with the real value.
Regards,
Daniel
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[Qemu-devel] [PATCH v3 14/18] trace: get rid of generated-events.h/generated-events.c, Daniel P. Berrange, 2016/09/19
[Qemu-devel] [PATCH v3 16/18] trace: push reading of events up a level to tracetool main, Daniel P. Berrange, 2016/09/19
[Qemu-devel] [PATCH v3 18/18] trace: introduce a formal group name for trace events, Daniel P. Berrange, 2016/09/19
Re: [Qemu-devel] [PATCH v3 00/18] Refactor trace to allow modular build, no-reply, 2016/09/19