[PATCH 5/6] printk: Minimize time zero output

[Mike Travis]

Reduce the length for time zero messages by only printing "[0] ".

v2: updated to apply to x86-tip

Signed-off-by: Mike Travis <travis@xxxxxxx>
Reviewed-by: Jack Steiner <steiner@xxxxxxx>
Reviewed-by: Robin Holt <holt@xxxxxxx>
---
 kernel/printk.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- linux.orig/kernel/printk.c
+++ linux/kernel/printk.c
@@ -735,9 +735,14 @@ static inline int printk_emit_time(void)
 	unsigned long microsec_rem;
 
 	t = cpu_clock(printk_cpu);
-	microsec_rem = do_div(t, 1000000000) / 1000;
-	tlen = sprintf(tbuf, "[%5lu.%06lu] ", (unsigned long)t, microsec_rem);
-
+	if (likely(t)) {
+		microsec_rem = do_div(t, 1000000000) / 1000;
+		tlen = sprintf(tbuf, "[%5lu.%06lu] ",
+					(unsigned long)t, microsec_rem);
+	} else {
+		/* reduce byte count in log when time is zero */
+		tlen = sprintf(tbuf, "[0] ");
+	}
 	for (tp = tbuf; tp < tbuf + tlen; tp++)
 		emit_log_char(*tp);
 

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