linux-kernel - Re: perf tools: Call graph from Intel BTS

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Date:	Fri, 11 Jul 2014 12:18:18 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	David Ahern <dsahern@...il.com>,
	"Shishkin, Alexander" <alexander.shishkin@...el.com>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: perf tools: Call graph from Intel BTS

Em Fri, Jul 11, 2014 at 05:36:41PM +0300, Adrian Hunter escreveu:
> There are many perf tools patches and it would be helpful to start
> considering how to get them into mainline.  Many need to wait for
> the driver, but others could be taken sooner.

We can go on looking at each of the patches to see which ones can be
cherry picked, i.e. the ones that are fixes and not related to the work
you're doing, like:

commit 244c87b15b124914827f3ce28d8e70c8d147c9d0
Author: Adrian Hunter <adrian.hunter@...el.com>
Date:   Wed Jun 11 09:33:17 2014 +0300

    perf tools: Fix the value used for unknown pids
    
    The value used for unknown pids cannot be zero
    because that is used by the "idle" task.
    Use -1 instead.  Also handle the unknown pid
    case when creating map groups.
    
    Note that, threads with an unknown pid should not
    occur because fork (or synthesized) events precede
    the thread's existence.
    
    Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

But then one by one they need to be reviewed to check if the changes were made
to the whole tools/perf/ tree and if perhaps something new came along since you
changed some assumption, like 0 meaning unknown thread, in the above patch:

[acme@...andy linux]$ find tools -name "*.[ch]" | xargs grep machine__findnew_thread | grep 0
tools/perf/util/session.c:	thread = machine__findnew_thread(&session->machines.host, 0, 0);
tools/perf/tests/thread-mg-share.c:	leader = machine__findnew_thread(machine, 0, 0);
tools/perf/tests/thread-mg-share.c:	t1     = machine__findnew_thread(machine, 0, 1);
tools/perf/tests/thread-mg-share.c:	t2     = machine__findnew_thread(machine, 0, 2);
tools/perf/tests/thread-mg-share.c:	t3     = machine__findnew_thread(machine, 0, 3);
[acme@...andy linux]$

So I think that one way to reduce the size of that branch is to do just that:
start fresh from tip/perf/core, and go cherry picking those patches, making sure that they
take into account the whole current tools/perf/ tree, then ask for this patch to be pulled.

You could then rebase the old branch on top of the resulting branch once it is
merged upstream, rinse repeat.

- Arnaldo
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