Re: [PATCH 3 of 3] xen: sched_credit: add some tracing

[Dario Faggioli <raistlin@linux.it>]

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On Tue, 2012-12-04 at 19:10 +0000, George Dunlap wrote: 
> On 03/12/12 16:35, Dario Faggioli wrote:
> > +            /* Avoid TRACE_* to avoid a lot of useless !tb_init_done checks */
> > +            for_each_cpu(cpu, &mask)
> > +            {
> > +                struct {
> > +                    unsigned cpu:8;
> > +                } d;
> > +                d.cpu = cpu;
> > +                trace_var(TRC_CSCHED_TICKLE, 0,
> > +                          sizeof(d),
> > +                          (unsigned char*)&d);
> 
> Why not just TRC_1D()? 
>
As I tried to explain in the comment, I just wanted to avoid checking
for !tb_init_done more than once, as this happens within a loop and, at
least potentially, there may be more CPUs to tickle (and thus more calls
to TRACE_1D). I take this comment of yours as you not thinking that is
something worthwhile, right? If so, I can definitely turn this into a
"standard" TRACE_1D() call.

> The tracing infrastructure can only set the size 
> at a granularity of 32-bit words anyway, and at this point cpu is 
> "unsigned int", which will be a single word.
> 
I know that. I just followed suit from sched_credit2.c, but I agree it's
quite pointless for just one single field. Even if we decide to leave
the direct call to trace_var, I'll kill the dummy struct.

> Other than that, everything looks good.
> 
Ok, thanks. :-)
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://retis.sssup.it/people/faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)



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