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Subject[PATCH v4 05/17] perf ftrace: add option '-m/--buffer-size' to set per-cpu buffer size
Date
This adds an option '-m/--buffer-size' to allow us set the size of per-cpu
tracing buffer.

Signed-off-by: Changbin Du <changbin.du@gmail.com>

---
v2: support units as a suffix.
---
tools/perf/Documentation/perf-ftrace.txt | 5 +++
tools/perf/builtin-ftrace.c | 56 +++++++++++++++++++++++-
2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
index e204bf6d50d8..98fe01d354d1 100644
--- a/tools/perf/Documentation/perf-ftrace.txt
+++ b/tools/perf/Documentation/perf-ftrace.txt
@@ -56,6 +56,11 @@ OPTIONS
Ranges of CPUs are specified with -: 0-2.
Default is to trace on all online CPUs.

+-m::
+--buffer-size::
+ Set the size of per-cpu tracing buffer, <size> is expected to
+ be a number with appended unit character - B/K/M/G.
+
-T::
--trace-funcs=::
Only trace functions given by the argument. Multiple functions
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 342861a1d152..348e2d960987 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -26,7 +26,7 @@
#include "thread_map.h"
#include "util/cap.h"
#include "util/config.h"
-
+#include "util/units.h"

struct perf_ftrace {
struct evlist *evlist;
@@ -38,6 +38,7 @@ struct perf_ftrace {
struct list_head graph_funcs;
struct list_head nograph_funcs;
int graph_depth;
+ unsigned long percpu_buffer_size;
};

struct filter_entry {
@@ -320,6 +321,21 @@ static int set_tracing_depth(struct perf_ftrace *ftrace)
return 0;
}

+static int set_tracing_percpu_buffer_size(struct perf_ftrace *ftrace)
+{
+ int ret;
+
+ if (ftrace->percpu_buffer_size == 0)
+ return 0;
+
+ ret = write_tracing_file_int("buffer_size_kb",
+ ftrace->percpu_buffer_size / 1024);
+ if (ret < 0)
+ return ret;
+
+ return 0;
+}
+
static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
{
char *trace_file;
@@ -384,6 +400,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
goto out_reset;
}

+ if (set_tracing_percpu_buffer_size(ftrace) < 0) {
+ pr_err("failed to set tracing per-cpu buffer size\n");
+ goto out_reset;
+ }
+
if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
goto out_reset;
@@ -503,6 +524,37 @@ static void delete_filter_func(struct list_head *head)
}
}

+static int parse_buffer_size(const struct option *opt,
+ const char *str, int unset)
+{
+ unsigned long *s = (unsigned long *)opt->value;
+ static struct parse_tag tags_size[] = {
+ { .tag = 'B', .mult = 1 },
+ { .tag = 'K', .mult = 1 << 10 },
+ { .tag = 'M', .mult = 1 << 20 },
+ { .tag = 'G', .mult = 1 << 30 },
+ { .tag = 0 },
+ };
+ unsigned long val;
+
+ if (unset) {
+ *s = 0;
+ return 0;
+ }
+
+ val = parse_tag_value(str, tags_size);
+ if (val != (unsigned long) -1) {
+ if (val < 1024) {
+ pr_err("buffer size too small, must larger than 1KB.");
+ return -1;
+ }
+ *s = val;
+ return 0;
+ }
+
+ return -1;
+}
+
int cmd_ftrace(int argc, const char **argv)
{
int ret;
@@ -542,6 +594,8 @@ int cmd_ftrace(int argc, const char **argv)
"Set nograph filter on given functions", parse_filter_func),
OPT_INTEGER('D', "graph-depth", &ftrace.graph_depth,
"Max depth for function graph tracer"),
+ OPT_CALLBACK('m', "buffer-size", &ftrace.percpu_buffer_size, "size",
+ "size of per cpu buffer", parse_buffer_size),
OPT_END()
};

--
2.25.1
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