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Subject[PATCH 06/21] perf report: Cache cumulative callchains
Date
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.

Tested-by: Arun Sharma <asharma@fb.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/hist.c | 43 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 5ebdc346bffb..c393f13789cb 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -716,7 +716,22 @@ 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;
}

@@ -726,6 +741,7 @@ 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;

he = __hists__add_entry(&evsel->hists, al, iter->parent, NULL, NULL,
@@ -734,6 +750,8 @@ iter_add_single_cumulative_entry(struct hist_entry_iter *iter,
if (he == NULL)
return -ENOMEM;

+ he_cache[iter->curr++] = he;
+
return hist_entry__inc_addr_samples(he, evsel->idx, al->addr);
}

@@ -758,7 +776,29 @@ 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,
@@ -766,6 +806,8 @@ iter_add_next_cumulative_entry(struct hist_entry_iter *iter,
if (he == NULL)
return -ENOMEM;

+ he_cache[iter->curr++] = he;
+
return hist_entry__inc_addr_samples(he, evsel->idx, al->addr);
}

@@ -779,6 +821,7 @@ iter_finish_cumulative_entry(struct hist_entry_iter *iter,
evsel->hists.stats.total_period += sample->period;
hists__inc_nr_events(&evsel->hists, PERF_RECORD_SAMPLE);

+ zfree(&iter->priv);
return 0;
}

--
1.7.11.7


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