tracing: Simplify print_graph_cpu()

print_graph_cpu() is little over-designed.

And "log10_all" may be wrong when there are holes in cpu_online_mask:
the max online cpu id > cpumask_weight(cpu_online_mask)

So change it by using a static column length for the cpu matching
nr_cpu_ids number of decimal characters.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A6EEE5E.2000001@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 4 insertions, 26 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index abf7c4ae2c8b..e30472da15d5 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -183,43 +183,19 @@ static void graph_trace_reset(struct trace_array *tr)
         unregister_ftrace_graph();
 }
 
-static inline int log10_cpu(int nb)
-{
-        if (nb / 100)
-                return 3;
-        if (nb / 10)
-                return 2;
-        return 1;
-}
+static int max_bytes_for_cpu;
 
 static enum print_line_t
 print_graph_cpu(struct trace_seq *s, int cpu)
 {
-        int i;
         int ret;
-        int log10_this = log10_cpu(cpu);
-        int log10_all = log10_cpu(cpumask_weight(cpu_online_mask));
-
 
         /*
          * 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)
-                        return TRACE_TYPE_PARTIAL_LINE;
-        }
-        ret = trace_seq_printf(s, "%d) ", cpu);
+        ret = trace_seq_printf(s, " %*d) ", max_bytes_for_cpu, cpu);
         if (!ret)
                 return TRACE_TYPE_PARTIAL_LINE;
 
@@ -919,6 +895,8 @@ static struct tracer graph_trace __read_mostly = {
 
 static __init int init_graph_trace(void)
 {
+        max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);
+
         return register_tracer(&graph_trace);
 }