scx_bpfland: improve cpufreq awareness #600
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Add hints for the cpufreq governor based on the selected scheduler's
performance profile and the current energy performance preference (EPP).
With this change applied the scheduler works as following:
scheduler profile (--primary-domain option):
- default:
- use all cores
- cpufreq: use default scaling factor
- powersave:
- use E-cores
- cpufreq: use min scaling factor
- performance:
- use P-cores
- cpufreq: use max scaling factor
- auto:
- EPP: power, powersave
- use E-cores
- cpufreq: use min scaling factor
- EPP: balance_power (typically battery-powered systems)
- use E-cores
- cpufreq: use default scaling factor
- EPP: balance_performance, performance
- use P-cores
- cpufreq: use max scaling factor
Signed-off-by: Andrea Righi <[email protected]>
When tasks are changing CPU affinity it is pointless to try to find an optimal idle CPU. In this case just skip the the idle CPU selection step and let the task being dispatched to a global DSQ if needed. Signed-off-by: Andrea Righi <[email protected]>
Always consider the turbo domain when running in "auto" mode.
Additionally, when the turbo domain is used, split the CPU idle
selection logic into two stages:
1) in ops.select_cpu(), provide the task with a second opportunity to
remain within the same LLC
2) in ops.enqueue(), perform another check for an idle CPU, allowing
the task to move to a different LLC if an idle CPU within the same
LLC is not available.
This allows tasks to stick more on turbo-boosted CPUs and CPUs within
the same LLC.
Signed-off-by: Andrea Righi <[email protected]>
hodgesds
reviewed
Sep 3, 2024
| }); | ||
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| res.unwrap_or_else(|_| "none".to_string()) | ||
| let energy_pref_path = |
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At some point maybe we can pull some of the cpu frequency governor into the topology helpers.
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Yes, that's a good idea. I'll send a separate PR for that.
BTW, unrelated but similar topic, it'd be nice to include also amd_pstate_highest_perf to the turbo cores logic.
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There's no "auto" mode when SCX scheduler is loaded and schedutil governor is used (there's no signal that the kernel side can use or even know). If you don't change anything, it'll just remain at the last setting. |
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Ah.. I was missing that, then I always need to set a value, I can't just ignore it (unless I actually want to keep the previous value). Ok, thanks @htejun I'll change the logic to take that aspect into account. |
In auto mode, rather than keeping the previous fixed cpuperf factor, dynamically calculate it based on CPU utilization and apply it before a task runs within its allocated time slot. Interactive tasks consistently receive the maximum scaling factor to ensure optimal performance. Signed-off-by: Andrea Righi <[email protected]>
htejun
approved these changes
Sep 3, 2024
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Provide a basic cpufreq control, based on the selected EPP and scheduler's performance profile.
Improve turbo boost CPU selection logic.