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Date: Fri, 22 May 2015 16:38:04 +0100
From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
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Subject: Re: [RFCv4 PATCH 22/34] sched: Calculate energy consumption of
 sched_group
Message-ID: <20150522153804.GF26396@e105550-lin.cambridge.arm.com>
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On Thu, May 21, 2015 at 08:57:04AM +0100, Kamalesh Babulal wrote:
> * Morten Rasmussen <morten.rasmussen@arm.com> [2015-05-12 20:38:57]:
> 
> [...]
> > +/*
> > + * cpu_norm_usage() returns the cpu usage relative to a specific capacity,
> > + * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
> > + * energy calculations. Using the scale-invariant usage returned by
> > + * get_cpu_usage() and approximating scale-invariant usage by:
> > + *
> > + *   usage ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
> > + *
> > + * the normalized usage can be found using the specific capacity.
> > + *
> > + *   capacity = capacity_orig * curr_freq/max_freq
> > + *
> > + *   norm_usage = running_time/time ~ usage/capacity
> > + */
> > +static unsigned long cpu_norm_usage(int cpu, unsigned long capacity)
> > +{
> > +	int usage = __get_cpu_usage(cpu);
> 
> __get_cpu_usage is introduced in next patch "sched: Extend sched_group_energy
> to test load-balancing decisions", applying the series with this patch as top
> most patch breaks the build.
> 
> kernel/sched/fair.c: In function ‘cpu_norm_usage’:
> kernel/sched/fair.c:4830:2: error: implicit declaration of function ‘__get_cpu_usage’ [-Werror=implicit-function-declaration]
>   int usage = __get_cpu_usage(cpu);
>   ^
> 
> Given that __get_cpu_usage(), take additional parameter - delta. get_cpu_usage()
> should have been used here.

Yes, you are right. Using get_cpu_usage() here instead should be
correct. I think it was right in RFCv3, I must have messed it up when I
moved around some of the patches :(

I will make sure to test the patch set is bisectable next time :)

Thanks,
Morten