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Date: Fri, 25 Feb 2011 12:06:36 -0600
From: Mike Travis <travis@sgi.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: David Rientjes <rientjes@google.com>, Jack Steiner <steiner@sgi.com>,
	Robin Holt <holt@sgi.com>, Len Brown <len.brown@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Yinghai Lu <yhlu.kernel@gmail.com>, linux-acpi@vger.kernel.org,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 3/4] printk: Minimize time zero output
Content-Disposition: inline; filename=minimize-time-zero-msgs
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--- linux.orig/kernel/printk.c
+++ linux/kernel/printk.c
@@ -745,12 +745,17 @@ static inline int printk_emit_time(void)
 	char tbuf[50], *tp;
 	unsigned tlen;
 	unsigned long long t;
-	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)) {
+		unsigned long 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);