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In order be able to compute the sizes of tasks consistently across all CPUs in a hybrid system, it is necessary to provide CPU capacity scaling information to the scheduler via arch_scale_cpu_capacity(). Moreover, the value returned by arch_scale_freq_capacity() for the given CPU must correspond to the arch_scale_cpu_capacity() return value for it, or utilization computations will be inaccurate. Add support for it through per-CPU variables holding the capacity and maximum-to-base frequency ratio (times SCHED_CAPACITY_SCALE) that will be returned by arch_scale_cpu_capacity() and used by scale_freq_tick() to compute arch_freq_scale for the current CPU, respectively. In order to avoid adding measurable overhead for non-hybrid x86 systems, which are the vast majority in the field, whether or not the new hybrid CPU capacity scaling will be in effect is controlled by a static key. This static key is set by calling arch_enable_hybrid_capacity_scale() which also allocates memory for the per-CPU data and initializes it. Next, arch_set_cpu_capacity() is used to set the per-CPU variables mentioned above for each CPU and arch_rebuild_sched_domains() needs to be called for the scheduler to realize that capacity-aware scheduling can be used going forward. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> # scale invariance Link: https://patch.msgid.link/10523497.nUPlyArG6x@rjwysocki.net [ rjw: Added parens to function kerneldoc comments ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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