[tip:perf/core] perf script: Add --max-stack knob

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  6125cc8dac432948a31df4d4ac20dd2d4f8c6c27
Gitweb:     http://git.kernel.org/tip/6125cc8dac432948a31df4d4ac20dd2d4f8c6c27
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Thu, 14 Apr 2016 18:15:18 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 14 Apr 2016 19:46:57 -0300

perf script: Add --max-stack knob

Works just like with 'perf report'. In some cases we may want to have
more than 127 entries, the default maximum.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-mqkz2p5ok2978gztb0vsnocc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/Documentation/perf-script.txt | 10 ++++++++++
 tools/perf/builtin-script.c              |  5 +++++
 2 files changed, 15 insertions(+)

diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
index 22ef393..4fc44c7 100644
--- a/tools/perf/Documentation/perf-script.txt
+++ b/tools/perf/Documentation/perf-script.txt
@@ -259,6 +259,16 @@ include::itrace.txt[]
 --full-source-path::
 	Show the full path for source files for srcline output.
 
+--max-stack::
+        Set the stack depth limit when parsing the callchain, anything
+        beyond the specified depth will be ignored. This is a trade-off
+        between information loss and faster processing especially for
+        workloads that can have a very long callchain stack.
+        Note that when using the --itrace option the synthesized callchain size
+        will override this value if the synthesized callchain size is bigger.
+
+        Default: 127
+
 --ns::
 	Use 9 decimal places when displaying time (i.e. show the nanoseconds)
 
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 875d84e..0e93282b 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -22,6 +22,7 @@
 #include "util/thread_map.h"
 #include "util/stat.h"
 #include <linux/bitmap.h>
+#include <linux/stringify.h>
 #include "asm/bug.h"
 #include "util/mem-events.h"
 
@@ -2027,6 +2028,10 @@ int cmd_script(int argc, const char **argv, const char *prefix __maybe_unused)
 		   "only consider symbols in these pids"),
 	OPT_STRING(0, "tid", &symbol_conf.tid_list_str, "tid[,tid...]",
 		   "only consider symbols in these tids"),
+	OPT_UINTEGER(0, "max-stack", &scripting_max_stack,
+		     "Set the maximum stack depth when parsing the callchain, "
+		     "anything beyond the specified depth will be ignored. "
+		     "Default: " __stringify(PERF_MAX_STACK_DEPTH)),
 	OPT_BOOLEAN('I', "show-info", &show_full_info,
 		    "display extended information from perf.data file"),
 	OPT_BOOLEAN('\0', "show-kernel-path", &symbol_conf.show_kernel_path,