The patch titled
init: skip calibration delay if previously done
has been added to the -mm tree. Its filename is
init-skip-calibration-delay-if-previously-done.patch
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------------------------------------------------------
Subject: init: skip calibration delay if previously done
From: Sameer Nanda <snanda@xxxxxxxxxxxx>
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.
Signed-off-by: Sameer Nanda <snanda@xxxxxxxxxxxx>
Cc: Phil Carmody <ext-phil.2.carmody@xxxxxxxxx>
Cc: Andrew Worsley <amworsley@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
init/calibrate.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff -puN init/calibrate.c~init-skip-calibration-delay-if-previously-done init/calibrate.c
--- a/init/calibrate.c~init-skip-calibration-delay-if-previously-done
+++ a/init/calibrate.c
@@ -246,11 +246,18 @@ recalibrate:
return lpj;
}
+DEFINE_PER_CPU(unsigned long, cpu_loops_per_jiffy) = { 0 };
+
void __cpuinit calibrate_delay(void)
{
static bool printed;
+ int this_cpu = smp_processor_id();
- if (preset_lpj) {
+ if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
+ loops_per_jiffy = per_cpu(cpu_loops_per_jiffy, this_cpu);
+ pr_info("Calibrating delay loop (skipped) "
+ "already calibrated this CPU previously.. ");
+ } else if (preset_lpj) {
loops_per_jiffy = preset_lpj;
if (!printed)
pr_info("Calibrating delay loop (skipped) "
@@ -268,6 +275,7 @@ void __cpuinit calibrate_delay(void)
pr_info("Calibrating delay loop... ");
loops_per_jiffy = calibrate_delay_converge();
}
+ per_cpu(cpu_loops_per_jiffy, this_cpu) = loops_per_jiffy;
if (!printed)
pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
loops_per_jiffy/(500000/HZ),
_
Patches currently in -mm which might be from snanda@xxxxxxxxxxxx are
init-skip-calibration-delay-if-previously-done.patch
init-skip-calibration-delay-if-previously-done-fix.patch
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