trace-cmd: Add an option to set saved_cmdlines_size
The tracing file saved_cmdlines_size allows setting the number of entries
that saved_cmdlines will contain. The latter is then dumped into the
trace.dat file to map PIDs with comm. The default value is 128.
Link: http://lore.kernel.org/linux-trace-devel/1573647257-317361-2-git-send-email-vincent.donnefort@arm.com
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/Documentation/trace-cmd-record.1.txt b/Documentation/trace-cmd-record.1.txt
index bb18e88..0d75e43 100644
--- a/Documentation/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd-record.1.txt
@@ -280,6 +280,12 @@
A value of one will only show where userspace enters the kernel but not any
functions called in the kernel. The default is zero, which means no limit.
+*--cmdlines-size* 'size'::
+ Set the number of entries the kernel tracing file "saved_cmdlines" can
+ contain. This file is a circular buffer which stores the mapping between
+ cmdlines and PIDs. If full, it leads to unresolved cmdlines ("<...>") within
+ the trace. The kernel default value is 128.
+
*--module* 'module'::
Filter a module's name in function tracing. It is equivalent to adding
':mod:module' after all other functions being filtered. If no other function
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 60f4d67..80b2234 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -229,6 +229,7 @@
int topt;
int do_child;
int run_command;
+ int saved_cmdlines_size;
};
static void add_reset_file(const char *file, const char *val, int prio)
@@ -1810,6 +1811,39 @@
}
}
+static void set_saved_cmdlines_size(struct common_record_context *ctx)
+{
+ int fd, len, ret = -1;
+ char *path, *str;
+
+ if (!ctx->saved_cmdlines_size)
+ return;
+
+ path = tracecmd_get_tracing_file("saved_cmdlines_size");
+ if (!path)
+ goto err;
+
+ reset_save_file(path, RESET_DEFAULT_PRIO);
+
+ fd = open(path, O_WRONLY);
+ tracecmd_put_tracing_file(path);
+ if (fd < 0)
+ goto err;
+
+ len = asprintf(&str, "%d", ctx->saved_cmdlines_size);
+ if (len < 0)
+ die("%s couldn't allocate memory", __func__);
+
+ if (write(fd, str, len) > 0)
+ ret = 0;
+
+ close(fd);
+ free(str);
+err:
+ if (ret)
+ warning("Couldn't set saved_cmdlines_size");
+}
+
static int trace_check_file_exists(struct buffer_instance *instance, char *file)
{
struct stat st;
@@ -5192,6 +5226,7 @@
OPT_date = 255,
OPT_module = 256,
OPT_nofifos = 257,
+ OPT_cmdlines_size = 258,
};
void trace_stop(int argc, char **argv)
@@ -5469,6 +5504,7 @@
{"by-comm", no_argument, NULL, OPT_bycomm},
{"ts-offset", required_argument, NULL, OPT_tsoffset},
{"max-graph-depth", required_argument, NULL, OPT_max_graph_depth},
+ {"cmdlines-size", required_argument, NULL, OPT_cmdlines_size},
{"no-filter", no_argument, NULL, OPT_no_filter},
{"debug", no_argument, NULL, OPT_debug},
{"quiet", no_argument, NULL, OPT_quiet},
@@ -5797,6 +5833,9 @@
if (!ctx->instance->max_graph_depth)
die("Could not allocate option");
break;
+ case OPT_cmdlines_size:
+ ctx->saved_cmdlines_size = atoi(optarg);
+ break;
case OPT_no_filter:
no_filter = true;
break;
@@ -5992,6 +6031,7 @@
enable_events(instance);
}
+ set_saved_cmdlines_size(ctx);
set_buffer_size();
update_plugins(type);
set_options();
diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c
index b5788f7..05ec021 100644
--- a/tracecmd/trace-usage.c
+++ b/tracecmd/trace-usage.c
@@ -56,6 +56,7 @@
" --func-stack perform a stack trace for function tracer\n"
" (use with caution)\n"
" --max-graph-depth limit function_graph depth\n"
+ " --cmdlines-size change kernel saved_cmdlines_size\n"
" --no-filter include trace-cmd threads in the trace\n"
" --proc-map save the traced processes address map into the trace.dat file\n"
" --user execute the specified [command ...] as given user\n"
