linux-kernel - Re: [PATCH 3/3] perf record/report: Process events in order

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Date:	Tue, 7 Dec 2010 08:54:46 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ian Munsie <imunsie@....ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 3/3] perf record/report: Process events in order

Em Tue, Dec 07, 2010 at 11:47:35AM +0100, Thomas Gleixner escreveu:
> On Tue, 7 Dec 2010, Ian Munsie wrote:
> > Makes sense. I did something similar in the report layer that I was
> > about to send when I saw this email, but this way we have a generic
> > solution for other parts of perf that might want this.
> > The problem here is that we only get the PERF_RECORD_HEADER_ATTR if perf
> > record has been piped somewhere, so running perf record <load>; perf
> > report on an unpatched kernel results in the COMM, MMAP, etc events
> > being processed last (timestamp -1ULL) and no userspace samples are
> > attributed at all:
> 
> Ok. We need to treat timestamp ~0ULL the same as timestamp 0ULL then.

Right.
  
> > > +    event__parse_sample(event, session, &sample);
> > > +    if (dump_trace)
> > > +        perf_session__print_tstamp(session, event, &sample);
> > 
> > Moving this here after the dump_printf("%#Lx [%#x]: PERF_RECORD_%s"...
> > changes the output of perf report -D in a bad way. Changing the spacing
> > in dump_printf can make up for it, or juggle the code around some more.
> 
> Crap. I wanted to restrict the sample parsing to the real events w/o
> having this magic comparison in place as we filter out the synth stuff
> in the switch case already. 
> 
> > How do you want to proceed? At this point either version of the patches
> > are pretty functionally equivelant. Mine does the perf report -D
> 
> Hmm. Arnaldo merged my version already.
> 
> > reordering as well, but that isn't really necessary to solve the bug.
> > Either way we only have a few minor fixups left.
> 
> Having time ordered output of -D needs more than fixing the time stamp
> issue. The dump_printf/dump_trace stuff is scattered all over the
> place. So that needs more code churn, as you want to output the non
> synth events when the ordered queue is drained.

We can fix that, but then it was supposed to be a dump, something as it
comes from the perf.data file.

Perhaps we need something new, that does ordered dumps, I think we can
just move all the dump_fprintf stuff to one place, and have calls for
those where it is now (unordered) and another one from the ordered
place, but looking at different debug variables?

- Arnaldo
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