[PATCH 10/28] perf report: Cache cumulative callchains

Namhyung Kim
2014-01-08T08:47:51Z

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.

Cc: Arun Sharma <asharma@fb.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-report.c | 54 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 06330736485b..087d01cac1aa 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -363,7 +363,27 @@ static int
iter_prepare_cumulative_entry(struct hist_entry_iter *iter __maybe_unused,
struct addr_location *al __maybe_unused)
{
+ struct callchain_cursor_node *node;
+ 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;
+
+ node = callchain_cursor_current(&callchain_cursor);
+ if (node == NULL)
+ return 0;
+
return 0;
}

@@ -373,6 +393,7 @@ 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,
@@ -381,6 +402,8 @@ 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);
}

@@ -408,8 +431,8 @@ iter_next_cumulative_entry(struct hist_entry_iter *iter,
goto out;
}

- if (al->map->groups == &iter->machine->kmaps) {
- if (machine__is_host(iter->machine)) {
+ if (al->map->groups == &al->machine->kmaps) {
+ if (machine__is_host(al->machine)) {
al->cpumode = PERF_RECORD_MISC_KERNEL;
al->level = 'k';
} else {
@@ -417,7 +440,7 @@ iter_next_cumulative_entry(struct hist_entry_iter *iter,
al->level = 'g';
}
} else {
- if (machine__is_host(iter->machine)) {
+ if (machine__is_host(al->machine)) {
al->cpumode = PERF_RECORD_MISC_USER;
al->level = '.';
} else if (perf_guest) {
@@ -440,7 +463,29 @@ 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,
@@ -448,6 +493,8 @@ 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);
}

@@ -461,6 +508,7 @@ 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