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The 'sched_energy_aware' sysctl is available for the admin to disable/enable energy aware scheduling(EAS). EAS is enabled only if few conditions are met by the platform. They are, asymmetric CPU capacity, no SMT, schedutil CPUfreq governor, frequency invariant load tracking etc. A platform may boot without EAS capability, but could gain such capability at runtime. For example, changing/registering the cpufreq governor to schedutil. At present, though platform doesn't support EAS, this sysctl returns 1 and it ends up calling build_perf_domains on write to 1 and NOP when writing to 0. That is confusing and un-necessary. Desired behavior would be to have this sysctl to enable/disable the EAS on supported platform. On non-supported platform write to the sysctl would return not supported error and read of the sysctl would return empty. So sched_energy_aware returns empty - EAS is not possible at this moment This will include EAS capable platforms which have at least one EAS condition false during startup, e.g. not using the schedutil cpufreq governor sched_energy_aware returns 0 - EAS is supported but disabled by admin. sched_energy_aware returns 1 - EAS is supported and enabled. User can find out the reason why EAS is not possible by checking info messages. sched_is_eas_possible returns true if the platform can do EAS at this moment. Signed-off-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Pierre Gondois <pierre.gondois@arm.com> Reviewed-by: Valentin Schneider <vschneid@redhat.com> Link: https://lore.kernel.org/r/20231009060037.170765-3-sshegde@linux.vnet.ibm.com |
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