tracing/function-graph-tracer: more output tweaks

Impact: prettify the output some more

Before:

0)           |     sys_read() {
0)      0.796 us |   fget_light();
0)           |       vfs_read() {
0)           |         rw_verify_area() {
0)           |           security_file_permission() {
------------8<---------- thread sshd-1755 ------------8<----------

After:

 0)               |  sys_read() {
 0)      0.796 us |    fget_light();
 0)               |    vfs_read() {
 0)               |      rw_verify_area() {
 0)               |        security_file_permission() {
 ------------------------------------------
 | 1)  migration/0--1  =>  sshd-1755
 ------------------------------------------

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 38 insertions, 7 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 596a3ee43053..894b50bca313 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -79,6 +79,19 @@ print_graph_cpu(struct trace_seq *s, int cpu)
         int log10_all = log10_cpu(cpus_weight_nr(cpu_online_map));
 
 
+        /*
+         * Start with a space character - to make it stand out
+         * to the right a bit when trace output is pasted into
+         * email:
+         */
+        ret = trace_seq_printf(s, " ");
+
+        /*
+         * Tricky - we space the CPU field according to the max
+         * number of online CPUs. On a 2-cpu system it would take
+         * a maximum of 1 digit - on a 128 cpu system it would
+         * take up to 3 digits:
+         */
         for (i = 0; i < log10_all - log10_this; i++) {
                 ret = trace_seq_printf(s, " ");
                 if (!ret)
@@ -86,7 +99,8 @@ print_graph_cpu(struct trace_seq *s, int cpu)
         }
         ret = trace_seq_printf(s, "%d) ", cpu);
         if (!ret)
-                        return TRACE_TYPE_PARTIAL_LINE;
+                return TRACE_TYPE_PARTIAL_LINE;
+
         return TRACE_TYPE_HANDLED;
 }
 
@@ -94,17 +108,34 @@ print_graph_cpu(struct trace_seq *s, int cpu)
 /* If the pid changed since the last trace, output this event */
 static int verif_pid(struct trace_seq *s, pid_t pid, int cpu)
 {
-        char *comm;
+        char *comm, *prev_comm;
+        pid_t prev_pid;
+        int ret;
 
         if (last_pid[cpu] != -1 && last_pid[cpu] == pid)
                 return 1;
 
+        prev_pid = last_pid[cpu];
         last_pid[cpu] = pid;
+
         comm = trace_find_cmdline(pid);
+        prev_comm = trace_find_cmdline(prev_pid);
 
-        return trace_seq_printf(s, "\n------------8<---------- thread %s-%d"
-                                    " ------------8<----------\n\n",
-                                    cpu, comm, pid);
+/*
+ * Context-switch trace line:
+
+ ------------------------------------------
+ | 1)  migration/0--1  =>  sshd-1755
+ ------------------------------------------
+
+ */
+        ret = trace_seq_printf(s,
+                " ------------------------------------------\n");
+        ret += trace_seq_printf(s, " | %d)  %s-%d  =>  %s-%d\n",
+                                  cpu, prev_comm, prev_pid, comm, pid);
+        ret += trace_seq_printf(s,
+                " ------------------------------------------\n\n");
+        return ret;
 }
 
 static bool
@@ -142,7 +173,7 @@ static inline int
 print_graph_duration(unsigned long long duration, struct trace_seq *s)
 {
         unsigned long nsecs_rem = do_div(duration, 1000);
-        return trace_seq_printf(s, "%4llu.%3lu us | ", duration, nsecs_rem);
+        return trace_seq_printf(s, "%4llu.%3lu us |  ", duration, nsecs_rem);
 }
 
 /* Signal a overhead of time execution to the output */
@@ -229,7 +260,7 @@ print_graph_entry_nested(struct ftrace_graph_ent_entry *entry,
         }
 
         /* No time */
-        ret = trace_seq_printf(s, "        |     ");
+        ret = trace_seq_printf(s, "            |  ");
 
         /* Function */
         for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++) {