Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 31 Jan 2018 10:56:31 +0100 | Subject | Re: [PATCH 5/8] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver |
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On 31 January 2018 at 10:50, Daniel Lezcano <daniel.lezcano@linaro.org> wrote: > On 31/01/2018 10:46, Vincent Guittot wrote: >> On 31 January 2018 at 10:33, Daniel Lezcano <daniel.lezcano@linaro.org> wrote: >>> On 31/01/2018 10:01, Vincent Guittot wrote: >>>> Hi Daniel, >>>> >>>> On 23 January 2018 at 16:34, Daniel Lezcano <daniel.lezcano@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.
Because you don't care of the CPU ordering to retrieve the data as they are stored per cpu directly
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