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scx_rustland: lowlatency improvements #59

Merged
merged 4 commits into from
Dec 31, 2023
Merged

scx_rustland: lowlatency improvements #59

merged 4 commits into from
Dec 31, 2023

Commits on Dec 31, 2023

  1. scx_rustland: enable SCX_OPS_ENQ_LAST 

    Make sure the scheduler is not activated if we are deadling with the
last task running.

This allows to consistency reduce scx_rustland CPU usage in systems that
are mostly idle (and avoid unnecessary power consumption).

Signed-off-by: Andrea Righi <[email protected]>
    Andrea Righi committed Dec 31, 2023
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  2. scx_rustland: always use dispatch_on_cpu() when possible 

    Use dispatch_on_cpu() when possible, so that all tasks dispatched by the
user-space scheduler gets the same priority, instead of having some of
them dispatched to the global DSQ and others dispatched to the per-CPU
DSQ.

Signed-off-by: Andrea Righi <[email protected]>
    Andrea Righi committed Dec 31, 2023
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  3. scx_rustland: bypass user-space scheduler for short-lived kthreads 

    Bypass the user-space scheduler for kthreads that still have more than
half of their runtime budget.

As they are likely to release the CPU soon, granting them a substantial
priority boost can enhance the overall system performance.

In the event that one of these kthreads turns into a CPU hog, it will
deplete its runtime budget and therefore it will be scheduled like
any other normal task through the user-space scheduler.

Signed-off-by: Andrea Righi <[email protected]>
    Andrea Righi committed Dec 31, 2023
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  4. scx_rustland: show the CPU where the scheduler is running 

    In the scheduler statistics reported periodically to stdout, instead of
showing "pid=0" for the CPU where the scheduler is running (like an idle
CPU), show "[self]".

This helps to identify exactly where the user-space scheduler is running
(when and where it migrates, etc.).

Signed-off-by: Andrea Righi <[email protected]>
    Andrea Righi committed Dec 31, 2023
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