linux-kernel - Re: [PATCH 04/18] Make cpu_tsc

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Message-ID: <4C456422.7030708@redhat.com>
Date:	Tue, 20 Jul 2010 03:53:54 -0500
From:	"Avi Kivity" <avi@...hat.com>
To:	"Zachary Amsden" <zamsden@...hat.com>
Cc:	"KVM" <kvm@...r.kernel.org>,
	"Marcelo Tosatti" <mtosatti@...hat.com>,
	"Glauber Costa" <glommer@...hat.com>,
	"Linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/18] Make cpu_tsc_khz updates use local CPU

On 07/19/2010 11:06 PM, Zachary Amsden wrote:
>>> +static void tsc_khz_changed(void *data)
>>>   {
>>> -    /* nothing */
>>> +    struct cpufreq_freqs *freq = data;
>>> +    unsigned long khz = 0;
>>> +
>>> +    if (data)
>>> +        khz = freq->new;
>>> +    else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
>>> +        khz = cpufreq_quick_get(raw_smp_processor_id());
>>> +    if (!khz)
>>> +        khz = tsc_khz;
>>> +    __get_cpu_var(cpu_tsc_khz) = khz;
>>>   }
>>
>> Do we really need to cache cpufreq_quick_get()?  If it's really 
>> quick, why not just use it everywhere instead of cacheing it?  Not a 
>> comment on this patch.
>>
>
>
> If cpufreq is compiled in, but disabled, it returns zero, so we need 
> some sort of logic.

Maybe it's better to put it into cpufreq_quick_get().  Inconsistent APIs 
that appear to work are bad.

-- 
error compiling committee.c: too many arguments to function

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