Re: [Qemu-devel] [PATCH 0/2] improve tracing

["Lluís Vilanova" <vilanova@ac.upc.edu>]

Vladimir Sementsov-Ogievskiy writes:

> 21.07.2017 20:04, Lluís Vilanova wrote:
>> Vladimir Sementsov-Ogievskiy writes:
>> 
>>> Current trace system have a drawback: parameters of trace functions
>>> are calculated even if corresponding tracepoint is disabled. Also, it
>>> looks like trace function are not actually inlined by compiler (at
>>> least for me).
>>> Here is a fix proposal: move from function call to macros. Patch 02
>>> is an example, of how to reduce extra calculations with help of
>>> patch 01.
>> The tracing functions *were* inlined last time I checked, although things
>> changed quite a lot since then. Not sure that will make a lot of difference in
>> terms of overall performance (needs measuring).
>> 
>> As for arguments, each trace event has a define TRACE_{NAME}_ENABLED that you
>> can use for that purpose. If this is not explained in tracing.txt, that is a
>> documentation bug.

> These macroses are about enable/disable traces statically. I'm saying about
> dynamic disable/enable.

Aha, I see. I think most events get passed already-calculated variables (usually
for other purposes), so I don't think it will have much of a performance
impact. Did you measure it?


Thanks,
  Lluis