Re: [Qemu-devel] [RFC PATCH 04/21] trace: enable the exec_tb trace events

[Alex Bennée]

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