On 31/01/2018 10:46, Vincent Guittot wrote:
> On 31 January 2018 at 10:33, Daniel Lezcano <daniel.lezc...@linaro.org> wrote:
>> On 31/01/2018 10:01, Vincent Guittot wrote:
>>> Hi Daniel,
>>>
>>> On 23 January 2018 at 16:34, Daniel Lezcano <daniel.lezc...@linaro.org>
>>> wrote:
>>
>> [ ... ] (please trim :)
>>
>>>> + /*
>>>> + * Each cooling device is per package. Each package
>>>> + * has a set of cpus where the physical number is
>>>> + * duplicate in the kernel namespace. We need a way to
>>>> + * address the waitq[] and tsk[] arrays with index
>>>> + * which are not Linux cpu numbered.
>>>> + *
>>>> + * One solution is to use the
>>>> + * topology_core_id(cpu). Other solution is to use the
>>>> + * modulo.
>>>> + *
>>>> + * eg. 2 x cluster - 4 cores.
>>>> + *
>>>> + * Physical numbering -> Linux numbering -> % nr_cpus
>>>> + *
>>>> + * Pkg0 - Cpu0 -> 0 -> 0
>>>> + * Pkg0 - Cpu1 -> 1 -> 1
>>>> + * Pkg0 - Cpu2 -> 2 -> 2
>>>> + * Pkg0 - Cpu3 -> 3 -> 3
>>>> + *
>>>> + * Pkg1 - Cpu0 -> 4 -> 0
>>>> + * Pkg1 - Cpu1 -> 5 -> 1
>>>> + * Pkg1 - Cpu2 -> 6 -> 2
>>>> + * Pkg1 - Cpu3 -> 7 -> 3
>>>
>>>
>>> I'm not sure that the assumption above for the CPU numbering is safe.
>>> Can't you use a per cpu structure to point to resources that are per
>>> cpu instead ? so you will not have to rely on CPU ordering
>>
>> Can you elaborate ? I don't get the part with the percpu structure.
>
> Something like:
>
> struct cpuidle_cooling_cpu {
> struct task_struct *tsk;
> wait_queue_head_t waitq;
> };
>
> DECLARE_PER_CPU(struct cpuidle_cooling_cpu *, cpu_data);
I got this part but I don't get how that fixes the ordering thing.
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