Re: [Qemu-devel] [PATCH for-2.8 v1 00/60] Modular build of trace event files

[Daniel P. Berrange]

On Fri, Sep 09, 2016 at 03:16:50PM +0200, Lluís Vilanova wrote:
> > The various  _DSTATE variables are still arbitrarily scattered in
> > memory, as opposed to in a contiguous cache friendly array, which
> > is one of the goals of Paolo's original change.
> 
> > That said, I'm unclear on how much of the performance win from
> > Paolo's change came from eliminating the struct field de-reference,
> > vs having the contiguous array. I'm guessing most of the win is
> > from the former, the latter only being important if we hit multiple
> > related tracepoints on close succession.
> 
> The latter can also be achieved by packing them all together in a single
> section, but I don't know if that's acceptable within portable QEMU code. For
> example:
> 
>   bool ___TRACE_EVENTNAME_DSTATE __attribute__((section("dstate_array")))

Acutally, it should be sufficient if we just generate all the dstate
variables in one place in the .c file - the compiler isn't going to
scatter a set of variables declared one after each other.

Regards,
Daniel
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