linux-kernel - Re: [PATCH 2/5] perf hists: Exchange order of comparing items when collapsing hists

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Date:	Fri, 7 Dec 2012 11:18:53 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/5] perf hists: Exchange order of comparing items when
 collapsing hists

On Fri, Dec 07, 2012 at 05:38:22PM +0900, Namhyung Kim wrote:
> Hi Arnaldo,
> 

SNIP

> @@ -739,6 +739,10 @@ static struct hist_entry *hists__add_dummy_entry(struct hists *hists,
>  
>                 cmp = hist_entry__collapse(he, pair);
>  
> +               if (sort__need_collapse)
> +                       cmp = hist_entry__collapse(he, pair);
> +               else
> +                       cmp = hist_entry__cmp(pair, he);
>                 if (!cmp)
>                         goto out;
>  
> @@ -772,7 +776,12 @@ static struct hist_entry *hists__find_entry(struct hists *hists,
>  
>         while (n) {
>                 struct hist_entry *iter = rb_entry(n, struct hist_entry, rb_node_in);
> -               int64_t cmp = hist_entry__collapse(iter, he);
> +               int64_t cmp;
> +
> +               if (sort__need_collapse)
> +                       cmp = hist_entry__collapse(iter, he);
> +               else
> +                       cmp = hist_entry__cmp(he, iter);
>  
>                 if (cmp < 0)
>                         n = n->rb_left;
> 
> It doesn't look good, especially hist_entry__collapse will be same as
> hist_entry__cmp if 'sort__need_collapse' is false.  If we can make the
> order consistent, it'd be converted to a sigle _collapse() call
> without the conditional.
> 
> Thanks,
> Namhyung

I've got non matching entries in diff after applying just patch 2/5,
and it's caused by missing he/iter swap in initial name resort in
insert_hist_entry_by_name function.

I understand that function goes away in your next patch while
add_hist_entry (swap ok) being the one doing initial name resort,
but still.. took me some time to figure this out ;)

jirka

---
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index b2e7d39..4dda6f4 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -285,7 +285,7 @@ static void insert_hist_entry_by_name(struct rb_root *root,
 	while (*p != NULL) {
 		parent = *p;
 		iter = rb_entry(parent, struct hist_entry, rb_node);
-		if (hist_entry__cmp(he, iter) < 0)
+		if (hist_entry__cmp(iter, he) < 0)
 			p = &(*p)->rb_left;
 		else
 			p = &(*p)->rb_right;
--
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