Re: [PATCH perf/core 00/22] perf refcnt debugger API and fixes

Namhyung Kim
2015-12-10T04:51:22Z

Hi Arnaldo and Masami,

On Wed, Dec 09, 2015 at 10:41:38AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Dec 09, 2015 at 11:10:48AM +0900, Masami Hiramatsu escreveu:
> > In this series I've also tried to fix some object leaks in perf top
> > and perf stat.
> > After applying this series, this reduced (not vanished) to 1/5.
> > ----
> > # ./perf top --stdio
> > q
> > exiting.
> > REFCNT: BUG: Unreclaimed objects found.
> > REFCNT: Total 866 objects are not reclaimed.
> > "dso" leaks 213 objects
> > "map" leaks 624 objects
> > "comm_str" leaks 12 objects
> > "thread" leaks 9 objects
> > "map_groups" leaks 8 objects
> > To see all backtraces, rerun with -v option
> > ----
> >
> > Actually, I'm still not able to fix all of the bugs. It seems that
> > hists has a bug that hists__delete_entries doesn't delete all the
> > entries because some entries are on hists->entries but others on
> > hists->entries_in. And I'm not so sure about hists.c.
> > Arnaldo, would you have any idea for this bug?
>
> I'll will audit the hists code, its all about collecting new entries
> into an rbtree to then move the last batch for merging with the
> previous, decayed ones while continuing to process a new batch in
> another thread.

Right. After processing is done, hist entries are in both of
hists->entries and hists->entries_in (or hists->entries_collapsed).
So I guess perf report does not have leaks on hists.

But for perf top, it's possible to have half-processed entries which
are only in hists->entries_in. Eventually they will go to the
hists->entries and get freed but they cannot be deleted by current
hists__delete_entries(). If we really care deleting all of those
half-processed entries, how about this?

Thanks,
Namhyung

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index fd179a068df7..08396a7fea23 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -270,6 +270,8 @@ static void hists__delete_entry(struct hists *hists, struct hist_entry *he)

if (sort__need_collapse)
rb_erase(&he->rb_node_in, &hists->entries_collapsed);
+ else
+ rb_erase(&he->rb_node_in, hists->entries_in);

--hists->nr_entries;
if (!he->filtered)
@@ -1589,11 +1591,33 @@ int __hists__init(struct hists *hists)
return 0;
}

+static void hists__delete_remaining_entries(struct rb_root *root)
+{
+ struct rb_node *node;
+ struct hist_entry *he;
+
+ while (!RB_EMPTY_ROOT(root)) {
+ node = rb_first(root);
+ rb_erase(node, root);
+
+ he = rb_entry(node, struct hist_entry, rb_node_in);
+ hist_entry__delete(he);
+ }
+}
+
+static void hists__delete_all_entries(struct hists *hists)
+{
+ hists__delete_entries(hists);
+ hists__delete_remaining_entries(&hists->entries_in_array[0]);
+ hists__delete_remaining_entries(&hists->entries_in_array[1]);
+ hists__delete_remaining_entries(&hists->entries_collapsed);
+}
+
static void hists_evsel__exit(struct perf_evsel *evsel)
{
struct hists *hists = evsel__hists(evsel);

- hists__delete_entries(hists);
+ hists__delete_all_entries(hists);
}

static int hists_evsel__init(struct perf_evsel *evsel)