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Re: [Qemu-devel] [RFC PATCH 04/21] trace: enable the exec_tb trace event
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [RFC PATCH 04/21] trace: enable the exec_tb trace events |
Date: |
Mon, 08 Oct 2018 10:41:45 +0100 |
User-agent: |
mu4e 1.1.0; emacs 26.1.50 |
Emilio G. Cota <address@hidden> writes:
> On Fri, Oct 05, 2018 at 16:48:53 +0100, Alex Bennée wrote:
>> Our performance isn't so critical that we can't spare a simple flag
>> check when we exec a TB considering everything else we check in the
>> outer loop.
>
> [I know this is just done to illustrate how function names
> in plugins can bind to tracing calls, but someone might
> get confused by expecting more from "exec_tb" than it
> actually does.]
>
> This flag check costs nothing because "exec_tb" is
> almost never called. The way it works right now, we
> need -d nochain for "exec_tb" to actually generate
> an event every time a TB executes.
I'll reword the commit a bit.
> IMO an eventual plugin API should let plugins decide whether
> to subscribe to the execution of a particular TB, when
> said TB is being translated, instead of providing
> an all-or-nothing switch.
Well we will want pre/post instruction translation hooks which would be
the obvious place to add this. Using -d nochain is a useful enough hack
for now.
>
> Thanks,
>
> E.
--
Alex Bennée
- [Qemu-devel] [RFC PATCH 00/21] Trace updates and plugin RFC, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 04/21] trace: enable the exec_tb trace events, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 01/21] util/log: allow -dfilter to stack, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 05/21] trace: keep a count of trace-point hits, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 18/21] linux-user: allow dumping of plugin status at end of run, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 10/21] qom/cpu: add a cpu_exit trace event, Alex Bennée, 2018/10/05
- [Qemu-devel] [RFC PATCH 12/21] configure: expose a plugin to the trace-backends, Alex Bennée, 2018/10/05