linux-kernel - Re: [PATCH] perf tools: Do not fail on processing out of order event

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Message-ID: <20141127144528.GL3808@redhat.com>
Date:	Thu, 27 Nov 2014 12:45:28 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf tools: Do not fail on processing out of order event

Em Thu, Nov 27, 2014 at 03:23:21PM +0100, Jiri Olsa escreveu:
> On Thu, Nov 27, 2014 at 12:16:26PM -0200, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Nov 27, 2014 at 03:07:07PM +0100, Jiri Olsa escreveu:
> > > On Thu, Nov 27, 2014 at 11:53:00AM -0200, Arnaldo Carvalho de Melo wrote:
> > > > Em Thu, Nov 27, 2014 at 11:56:03AM +0100, Ingo Molnar escreveu:
> > > > > Arnaldo, I suppose the fix will go upstream via your tree, as a 
> > > > > pull request for v3.18 fixes?
> > 
> > > > Right, I can do that.
> > 
> > > > And I agree with the "expected" for events that are out of the current
> > > > reordering window, i.e. we can't insert something into previous windows,
> > > > so those are, humm, what would be a good name:
> > > > stats->out_of_reordering_window, while stats->reordered, would be for
> > > > events that were found out of order, but were successfully sorted as
> > > > part of a flush operation, right?
> >  
> > > the forced flush is when we find out we crossed the allowed allocation
> > > space for the samples queue.. so we take the half of the sorted queue
> > > and flush it.. for this case we break the flushing logic and we might
> > 
> > Well, we make it more likely than without a forced flush to find out of
> > order events, because the window suddenly became smaller, its like we
> > found a FLUSH event right there, no?
 
> yep, still I dont see the need to count those 2 cases separately,
> both these types (of out of order event) have same implications
> for the report

Ok, I misundertood it when thinking it was about reordered events inside
a flush window versus events for a previous, closed flush window.

Yeah, if we detect events for a previous flush window in a forced flush
or in a normal flush, its all the same: events we can't consider anymore
because they are for a closed (old) flush window.

- Arnaldo
 
> jirka
> 
> > 
> > > (probably just in theory) get out of order events
> >  
> > > but IMO both cases of out of order event are equal.. we dont do
> > > anything special for forced flushed AFAIK
> > 
> > - Arnaldo
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