Re: cpufreq issue with K8 performance governor

["Peter Oruba" <peter.oruba@amd.com>]

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Am Dienstag, 29. Mai 2007 18:06:21 schrieben Sie:
> On Tue, May 29, 2007 at 03:47:00PM +0200, Peter Oruba wrote:
>  > Dave,
>  > 
>  > I am contacting you regarding a frequency scaling issue that I encountered with the performance governor in combination with CPU hotplug. In cpufreq.c CPU frequency is reduced to its 
>  > minimum before the CPU gets unregistered and set offline. Does that have a particular reason? Since the (k8-)governor does not monitor CPU frequency that setting also applies then to the remaining CPU
>  > as well and lets the system run on the lowest frequency although performance is chose as the policy.
>  > 
>  > ---
>  > static int cpufreq_cpu_callback(struct notifier_block *nfb,
>  >                                         unsigned long action, void *hcpu)
>  > {
>  > 
>  > [......]
>  > 
>  >                 case CPU_DOWN_PREPARE_FROZEN:
>  >                         if (unlikely(lock_policy_rwsem_write(cpu)))
>  >                                 BUG();
>  > 
>  >                         policy = cpufreq_cpu_data[cpu];
>  >                         if (policy) {
>  >                                 __cpufreq_driver_target(policy, policy->min,
>  >                                                 CPUFREQ_RELATION_H);
>  >                         }
>  >                         __cpufreq_remove_dev(sys_dev);
> 
> This is the path taken when we call suspend.
> To be honest, I doubt that reducing the speed has any benefit at all,
> as we're about to put the CPU to sleep anyway.
> 
> (btw, in future sending questions to cpufreq@lists.linux.org.uk is a better
>  idea. The subsystem is sufficiently complex that at times, others can
>  answer questions better than I can, especially with the various
>  implementations all being subtley different).
> 
> Thanks,
> 
> 	Dave
> 
Okay, removing the __cpufreq_driver_target call would solve would obviously solve that problem (which btw also exists on Core2, as I tested a couple of minutes ago). Is it planned to be changed 
in the near future?

Thanks,
Peter


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