Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 31 Jan 2018 10:46:01 +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 10:33, 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);
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