From 7afe1845dd1e7c90828c942daed7e57ffa7c38d6 Mon Sep 17 00:00:00 2001
From: Sameer Nanda <snanda@chromium.org>
Date: Mon, 25 Jul 2011 17:13:29 -0700
Subject: [PATCH] init: skip calibration delay if previously done
For each CPU, do the calibration delay only once. For subsequent calls,
use the cached per-CPU value of loops_per_jiffy.
This saves about 200ms of resume time on dual core Intel Atom N5xx based
systems. This helps bring down the kernel resume time on such systems
from about 500ms to about 300ms.
[akpm@linux-foundation.org: make cpu_loops_per_jiffy static]
[akpm@linux-foundation.org: clean up message text]
[akpm@linux-foundation.org: fix things up after upstream rmk changes]
Signed-off-by: Sameer Nanda <snanda@chromium.org>
Cc: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Andrew Worsley <amworsley@gmail.com>
Cc: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
init/calibrate.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/init/calibrate.c b/init/calibrate.c
index aae2f40fea4cb..24df7976816c6 100644
--- a/init/calibrate.c
+++ b/init/calibrate.c
@@ -9,6 +9,7 @@
#include <linux/init.h>
#include <linux/timex.h>
#include <linux/smp.h>
+#include <linux/percpu.h>
unsigned long lpj_fine;
unsigned long preset_lpj;
@@ -243,12 +244,19 @@ static unsigned long __cpuinit calibrate_delay_converge(void)
return lpj;
}
+static DEFINE_PER_CPU(unsigned long, cpu_loops_per_jiffy) = { 0 };
+
void __cpuinit calibrate_delay(void)
{
unsigned long lpj;
static bool printed;
+ int this_cpu = smp_processor_id();
- if (preset_lpj) {
+ if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
+ lpj = per_cpu(cpu_loops_per_jiffy, this_cpu);
+ pr_info("Calibrating delay loop (skipped) "
+ "already calibrated this CPU");
+ } else if (preset_lpj) {
lpj = preset_lpj;
if (!printed)
pr_info("Calibrating delay loop (skipped) "
@@ -266,6 +274,7 @@ void __cpuinit calibrate_delay(void)
pr_info("Calibrating delay loop... ");
lpj = calibrate_delay_converge();
}
+ per_cpu(cpu_loops_per_jiffy, this_cpu) = lpj;
if (!printed)
pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
lpj/(500000/HZ),
--
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