linux-kernel - Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)

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Message-ID: <20151214175242.GV6843@kernel.org>
Date:	Mon, 14 Dec 2015 14:52:42 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	David Ahern <dsahern@...il.com>, Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCHSET 00/16] perf top: Add multi-thread support (v1)

Em Mon, Dec 14, 2015 at 05:41:30PM +0100, Peter Zijlstra escreveu:
> On Mon, Dec 14, 2015 at 01:26:55PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Dec 14, 2015 at 07:55:32AM -0700, David Ahern escreveu:
> > > On 12/14/15 2:38 AM, Ingo Molnar wrote:
> > > >
> > > >>And in an unrelated note, I absolutely detest --buildid being the
> > > >>default, it makes perf-record blow chunks.
> 
> > Multiple things here, .debug/ should be size limited, and buildid
> > processing doesn't need necessarily to store things in that cache, I bet
> > what PeterZ is complaining about is the reprocessing of events at the
> > end of the session, to find out about the PERF_RECORD_MMAP* events to
> > then read the build-ids and insert then into the perf.data file header.
> > 
> 
> Yeah, its the reprocessing that is taking forever.. On my moderately
> sized system with 40 CPUs, the reprocessing is taking about as long as
> the actual workload, which is tedious.

Right, I thought about using some dummy event for tracking mmaps, which
I think is a technique used by the Intel PT code (well, there it uses it
for sched_switches) will check...
 
> Once I figured out what was happening Jiri was quick to point out I
> should be using -B.

Right, we have to have sane behaviour by default, damn long/high freq
workloads, duh ;-)

- Arnaldo
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