tracing/function-graph-tracer: improve duration output

Impact: better trace output of duration for long calls

The old duration output didn't exceeded 9999.999 us to fit the column
and the nanosecs were always 3 numbers. As Ingo suggested, it's better
to have the whole microseconds elapsed time and shift the nanosecs precision
if needed to fit the maximum 7 numbers. And usec need more number, the case
should be rare and important enough to break a bit the column alignment to
show it.

So, depending of the duration value, we now have these patterns:

    u.nnn us
   uu.nnn us
  uuu.nnn us
 uuuu.nnn us
 uuuuu.nn us
 uuuuuu.n us
 uuuuuuuu..... us

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 43 insertions, 12 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 23e19d2dbd06..c66578f2fdc2 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -232,11 +232,50 @@ trace_branch_is_leaf(struct trace_iterator *iter,
 }
 
 
-static inline int
+static enum print_line_t
 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);
+        /* log10(ULONG_MAX) + '\0' */
+        char msecs_str[21];
+        char nsecs_str[5];
+        int ret, len;
+        int i;
+
+        sprintf(msecs_str, "%lu", (unsigned long) duration);
+
+        /* Print msecs */
+        ret = trace_seq_printf(s, msecs_str);
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        len = strlen(msecs_str);
+
+        /* Print nsecs (we don't want to exceed 7 numbers) */
+        if (len < 7) {
+                snprintf(nsecs_str, 8 - len, "%03lu", nsecs_rem);
+                ret = trace_seq_printf(s, ".%s", nsecs_str);
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+                len += strlen(nsecs_str);
+        }
+
+        ret = trace_seq_printf(s, " us ");
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
+        /* Print remaining spaces to fit the row's width */
+        for (i = len; i < 7; i++) {
+                ret = trace_seq_printf(s, " ");
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+        }
+
+        ret = trace_seq_printf(s, "|  ");
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+        return TRACE_TYPE_HANDLED;
+
 }
 
 /* Signal a overhead of time execution to the output */
@@ -273,10 +312,6 @@ print_graph_entry_leaf(struct trace_iterator *iter,
         call = &entry->graph_ent;
         duration = graph_ret->rettime - graph_ret->calltime;
 
-        /* Must not exceed 8 characters: 9999.999 us */
-        if (duration > 10000000ULL)
-                duration = 9999999ULL;
-
         /* Overhead */
         if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERHEAD) {
                 ret = print_graph_overhead(duration, s);
@@ -286,7 +321,7 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 
         /* Duration */
         ret = print_graph_duration(duration, s);
-        if (!ret)
+        if (ret == TRACE_TYPE_PARTIAL_LINE)
                 return TRACE_TYPE_PARTIAL_LINE;
 
         /* Function */
@@ -387,10 +422,6 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
         int ret;
         unsigned long long duration = trace->rettime - trace->calltime;
 
-        /* Must not exceed 8 characters: xxxx.yyy us */
-        if (duration > 10000000ULL)
-                duration = 9999999ULL;
-
         /* Pid */
         if (verif_pid(s, ent->pid, cpu) == TRACE_TYPE_PARTIAL_LINE)
                 return TRACE_TYPE_PARTIAL_LINE;
@@ -422,7 +453,7 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
 
         /* Duration */
         ret = print_graph_duration(duration, s);
-        if (!ret)
+        if (ret == TRACE_TYPE_PARTIAL_LINE)
                 return TRACE_TYPE_PARTIAL_LINE;
 
         /* Closing brace */