trace-cmd: top: A new interface to detect peak memory

A new interface "trace-cmd top" has been introduced in this patch to
know peak memory usage of any task.

$ trace-cmd top -s "/tmp/socket"
It will start to gather statistics of all the process which will be
scheduled after this command execution.
$ trace-cmd top -p "/tmp/socket"
It will print peak memory usage(in KB) against each scheduled task.
$ trace-cmd top -e "/tmp/socket"
It will print peak memory usage(in KB) against each scheduled task and
will stop gathering statistics. It will also kill the child process
initiated by -s option.

 # ./trace-cmd top -s "/tmp/socket"
 # ./trace-cmd top -e "/tmp/socket"

pid             comm            peak memory(in KB)
37              rcuos/3                 0
1979            gnome-shell             374444
6286            bash                    6444
7972            trace-cmd               204
10244           thunderbird             830632
10264           Socket Thread           830632
10281           Timer                   830632
16806           kworker/1:0             0
21528           firefox                 1747356
32110           minicom                 6988

Signed-off-by: Pratyush Anand <panand@redhat.com>

Makefile

@@ -331,7 +331,7 @@ TRACE_GUI_OBJS = trace-filter.o trace-compat.o trace-filter-hash.o trace-dialog.
 		trace-xml.o
 TRACE_CMD_OBJS = trace-cmd.o trace-record.o trace-read.o trace-split.o trace-listen.o \
 	 trace-stack.o trace-hist.o trace-mem.o trace-snapshot.o trace-stat.o \
-	 trace-hash.o trace-profile.o trace-stream.o
+	 trace-hash.o trace-profile.o trace-stream.o trace-top.o
 TRACE_VIEW_OBJS = trace-view.o trace-view-store.o
 TRACE_GRAPH_OBJS = trace-graph.o trace-plot.o trace-plot-cpu.o trace-plot-task.o
 TRACE_VIEW_MAIN_OBJS = trace-view-main.o $(TRACE_VIEW_OBJS) $(TRACE_GUI_OBJS)

trace-cmd.c

@@ -495,6 +495,10 @@ int main (int argc, char **argv)
 		trace_stat(argc, argv);
 		exit(0);
 
+	} else if (strcmp(argv[1], "top") == 0) {
+		trace_top(argc, argv);
+		exit(0);
+
 	} else if (strcmp(argv[1], "options") == 0) {
 		show_plugin_options();
 		exit(0);

trace-local.h

@@ -74,6 +74,8 @@ void trace_mem(int argc, char **argv);
 
 void trace_stat(int argc, char **argv);
 
+void trace_top(int argc, char **argv);
+
 struct hook_list;
 
 int trace_profile_record(struct tracecmd_input *handle,
@@ -184,5 +186,6 @@ void update_first_instance(struct buffer_instance *instance, int topt);
 
 void show_instance_file(struct buffer_instance *instance, const char *name);
 int count_cpus(void);
+char *read_file(char *file, int *psize);
 
 #endif /* __TRACE_LOCAL_H */

trace-record.c

@@ -3323,7 +3323,7 @@ static char *read_instance_file(struct buffer_instance *instance, char *file, in
 	return buf;
 }
 
-static char *read_file(char *file, int *psize)
+char *read_file(char *file, int *psize)
 {
 	return read_instance_file(&top_instance, file, psize);
 }