From: Namhyung Kim <namhyung@kernel.org>
Date: Wed, 15 Jun 2022 16:32:21 +0000 (-0700)
Subject: perf record: Allow to specify max stack depth of fp callchain
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=7cb2a53f7f413734734bac214c4855e9863b9853;p=linux.git

perf record: Allow to specify max stack depth of fp callchain

Currently it has no interface to specify the max stack depth for perf
record.  Extend the command line parameter to accept a number after
'fp' to specify the depth like '--call-graph fp,32'.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220615163222.1275500-7-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 6bd6d07021bae..099817ef5150d 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -275,6 +275,11 @@ OPTIONS
 	User can change the size by passing the size after comma like
 	"--call-graph dwarf,4096".
 
+	When "fp" recording is used, perf tries to save stack enties
+	up to the number specified in sysctl.kernel.perf_event_max_stack
+	by default.  User can change the number by passing it after comma
+	like "--call-graph fp,32".
+
 -q::
 --quiet::
 	Don't print any message, useful for scripting.
diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 5c27a4b2e7a72..7e663673f79f9 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -31,6 +31,7 @@
 #include "callchain.h"
 #include "branch.h"
 #include "symbol.h"
+#include "util.h"
 #include "../perf.h"
 
 #define CALLCHAIN_PARAM_DEFAULT			\
@@ -266,12 +267,17 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
 	do {
 		/* Framepointer style */
 		if (!strncmp(name, "fp", sizeof("fp"))) {
-			if (!strtok_r(NULL, ",", &saveptr)) {
-				param->record_mode = CALLCHAIN_FP;
-				ret = 0;
-			} else
-				pr_err("callchain: No more arguments "
-				       "needed for --call-graph fp\n");
+			ret = 0;
+			param->record_mode = CALLCHAIN_FP;
+
+			tok = strtok_r(NULL, ",", &saveptr);
+			if (tok) {
+				unsigned long size;
+
+				size = strtoul(tok, &name, 0);
+				if (size < (unsigned) sysctl__max_stack())
+					param->max_stack = size;
+			}
 			break;
 
 		/* Dwarf style */