linux-kernel - Re: [PATCH] init: skip calibration delay if previously done

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Date:	Fri, 03 Jun 2011 14:08:01 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Sameer Nanda <snanda@...omium.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	ext-phil.2.carmody@...ia.com, Tim.Deegan@...rix.com,
	jbeulich@...ell.com, snanda@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init: skip calibration delay if previously done

On 06/03/2011 02:00 PM, Andrew Morton wrote:
> On Tue, 24 May 2011 16:19:06 -0700
> Sameer Nanda<snanda@...omium.org>  wrote:
>
>> 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@...omium.org>
>> ---
>>   init/calibrate.c |   10 +++++++++-
>>   1 files changed, 9 insertions(+), 1 deletions(-)
>>
>> diff --git a/init/calibrate.c b/init/calibrate.c
>> index 76ac919..47d3408 100644
>> --- a/init/calibrate.c
>> +++ b/init/calibrate.c
>> @@ -183,11 +183,18 @@ 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.. ");

That wording seems a little redundant, and there are two '.' at the end.

How about:
s/"already calibrated this CPU previously.. "/", this CPU previously 
calibrated."/

David Daney
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