linux-kernel - Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression

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Message-ID: <52B316FF.50906@zytor.com>
Date:	Thu, 19 Dec 2013 07:55:43 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>, Len Brown <lenb@...nel.org>
CC:	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression

On 12/19/2013 04:22 AM, Ingo Molnar wrote:
>> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
>> index 92d1206..f80b700 100644
>> --- a/drivers/idle/intel_idle.c
>> +++ b/drivers/idle/intel_idle.c
>> @@ -377,6 +377,9 @@ static int intel_idle(struct cpuidle_device *dev,
>>  
>>  	if (!current_set_polling_and_test()) {
>>  
>> +		if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
>> +			clflush((void *)&current_thread_info()->flags);
>> +
>>  		__monitor((void *)&current_thread_info()->flags, 0, 0);
> 
> I don't think either of these casts to '(void *)' is needed, both the 
> clflush() and __monitor() will take pointers.

__monitor() currently doesn't, which is idiotic.

	-hpa

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