perf report: Cache cumulative callchains

It is possble that a callchain has cycles or recursive calls.  In that
case it'll end up having entries more than 100% overhead in the
output.  In order to prevent such entries, cache each callchain node
and skip if same entry already cumulated.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arun Sharma <asharma@fb.com>
Tested-by: Rodrigo Campos <rodrigo@sdfg.com.ar>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1401335910-16832-8-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 37c28fc13dc3..bf03db528db6 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -700,7 +700,22 @@ static int
 iter_prepare_cumulative_entry(struct hist_entry_iter *iter __maybe_unused,
                               struct addr_location *al __maybe_unused)
 {
+        struct hist_entry **he_cache;
+
         callchain_cursor_commit(&callchain_cursor);
+
+        /*
+         * This is for detecting cycles or recursions so that they're
+         * cumulated only one time to prevent entries more than 100%
+         * overhead.
+         */
+        he_cache = malloc(sizeof(*he_cache) * (PERF_MAX_STACK_DEPTH + 1));
+        if (he_cache == NULL)
+                return -ENOMEM;
+
+        iter->priv = he_cache;
+        iter->curr = 0;
+
         return 0;
 }
 
@@ -710,6 +725,7 @@ iter_add_single_cumulative_entry(struct hist_entry_iter *iter,
 {
         struct perf_evsel *evsel = iter->evsel;
         struct perf_sample *sample = iter->sample;
+        struct hist_entry **he_cache = iter->priv;
         struct hist_entry *he;
         int err = 0;
 
@@ -720,6 +736,7 @@ iter_add_single_cumulative_entry(struct hist_entry_iter *iter,
                 return -ENOMEM;
 
         iter->he = he;
+        he_cache[iter->curr++] = he;
 
         /*
          * The iter->he will be over-written after ->add_next_entry()
@@ -754,7 +771,29 @@ iter_add_next_cumulative_entry(struct hist_entry_iter *iter,
 {
         struct perf_evsel *evsel = iter->evsel;
         struct perf_sample *sample = iter->sample;
+        struct hist_entry **he_cache = iter->priv;
         struct hist_entry *he;
+        struct hist_entry he_tmp = {
+                .cpu = al->cpu,
+                .thread = al->thread,
+                .comm = thread__comm(al->thread),
+                .ip = al->addr,
+                .ms = {
+                        .map = al->map,
+                        .sym = al->sym,
+                },
+                .parent = iter->parent,
+        };
+        int i;
+
+        /*
+         * Check if there's duplicate entries in the callchain.
+         * It's possible that it has cycles or recursive calls.
+         */
+        for (i = 0; i < iter->curr; i++) {
+                if (hist_entry__cmp(he_cache[i], &he_tmp) == 0)
+                        return 0;
+        }
 
         he = __hists__add_entry(&evsel->hists, al, iter->parent, NULL, NULL,
                                 sample->period, sample->weight,
@@ -763,6 +802,7 @@ iter_add_next_cumulative_entry(struct hist_entry_iter *iter,
                 return -ENOMEM;
 
         iter->he = he;
+        he_cache[iter->curr++] = he;
 
         return 0;
 }
@@ -771,7 +811,9 @@ static int
 iter_finish_cumulative_entry(struct hist_entry_iter *iter,
                              struct addr_location *al __maybe_unused)
 {
+        zfree(&iter->priv);
         iter->he = NULL;
+
         return 0;
 }