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Commit b4d3c8bd authored by Namhyung Kim's avatar Namhyung Kim Committed by Jiri Olsa
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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: default avatarNamhyung Kim <namhyung@kernel.org>
Tested-by: default avatarArun Sharma <asharma@fb.com>
Tested-by: default avatarRodrigo 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: default avatarJiri Olsa <jolsa@kernel.org>
parent c7405d85

tools/perf/util/hist.c

+42 −0
Original line number Diff line number Diff line
@@ -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;

}