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From: Andres Freund <andres@anarazel.de>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: "perf hists browser: Support flat callchains" appears to have broken parent reporting
Date: Wed, 30 Mar 2016 16:19:26 +0200	[thread overview]
Message-ID: <20160330141926.GA5242@awork2.anarazel.de> (raw)
In-Reply-To: <20160330134634.GA3420@kernel.org>

On 2016-03-30 10:46:34 -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Mar 30, 2016 at 02:34:18PM +0200, Andres Freund escreveu:
> > Hi,
> > 
> > 4b3a3212233a - "perf hists browser: Support flat callchains" seems to
> > have broken callchain display in tui mode when using !flat mode, or at
> > least changed it in an unintended manner.
> 
> humm, at first I thought this would be related to --percent-limit...

I'm not using --percent-limit. Just to be sure, I did explicitly set it
to various values, and it looks unrelated.

> What tree/branch are you using? Can you try pressing 'L' to play with
> the percent limit?

I'm primarily using linus' tree, and bisected the behavioural down to
that individual commit.

It's somewhat weird that --stdio doesn't show the problem, but --tui
does. Hm.


I don't know the perf code at all, but skimming through the commit, the
following hunk looks suspicious:

@@ -263,7 +295,7 @@ static void callchain_node__init_have_children(struct callchain_node *node,
    chain = list_entry(node->val.next, struct callchain_list, list);
    chain->has_children = has_sibling;
 
-   if (!list_empty(&node->val)) {
+   if (node->val.next != node->val.prev) {
        chain = list_entry(node->val.prev, struct callchain_list, list);
        chain->has_children = !RB_EMPTY_ROOT(&node->rb_root);
    }

Reverting that individual change fixes things.  I'm not actually sure
what the post 4b3a3212233a version actually tests for?


I think that actually explains why stdio works - nodes are always
unfolded in it, thus ->has_children isn't looked at.

Andres

  reply	other threads:[~2016-03-30 14:19 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-30 12:34 "perf hists browser: Support flat callchains" appears to have broken parent reporting Andres Freund
2016-03-30 13:46 ` Arnaldo Carvalho de Melo
2016-03-30 14:19   ` Andres Freund [this message]
2016-03-30 16:00     ` Namhyung Kim
2016-03-30 19:02       ` Andres Freund
2016-03-31  6:33         ` [tip:perf/urgent] perf hists: Fix determination of a callchain node's childlessness tip-bot for Andres Freund
2016-04-16 19:46           ` Andres Freund
2016-04-18 14:07             ` Arnaldo Carvalho de Melo
2016-04-18 14:25           ` Andres Freund
2016-05-02 22:17             ` Greg KH
2016-05-02 22:25               ` Andres Freund
2016-05-02 23:24                 ` Greg KH
2016-05-02 23:34                   ` Andres Freund
2016-03-30 21:07       ` "perf hists browser: Support flat callchains" appears to have broken parent reporting Arnaldo Carvalho de Melo

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