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rt: make the LIFO slot in the multi-threaded scheduler stealable #4941

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carllerche opened this issue Aug 24, 2022 · 2 comments
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rt: make the LIFO slot in the multi-threaded scheduler stealable #4941

carllerche opened this issue Aug 24, 2022 · 2 comments
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A-tokio Area: The main tokio crate C-feature-request Category: A feature request. M-runtime Module: tokio/runtime

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@carllerche
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The multi-threaded scheduler includes a per-worker LIFO slot used to store the last scheduled task. This can improve certain usage patterns, especially message passing between tasks. However, this LIFO slot is not currently stealable.

As a temporary workaround, #4936 adds an unstable configuration option to disable the LIFO slot.
@carllerche carllerche added A-tokio Area: The main tokio crate C-feature-request Category: A feature request. labels Aug 24, 2022
@carllerche carllerche mentioned this issue Aug 24, 2022
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carllerche added a commit that referenced this issue Aug 24, 2022
@carllerche
rt: add unstable option to disable the LIFO slot (#4936)
b023522 
The multi-threaded scheduler includes a per-worker LIFO slot to
store the last scheduled task. This can improve certain usage patterns,
especially message passing between tasks. However, this LIFO slot is not
currently stealable.

Eventually, the LIFO slot **will** become stealable. However, as a
stop-gap, this unstable option lets users disable the LIFO task when
doing so improves their application's overall performance.

Refs: #4941
@Darksonn Darksonn added the M-runtime Module: tokio/runtime label Aug 25, 2022
@Darksonn Darksonn mentioned this issue Dec 14, 2022
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@MortenLohne
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Is there any further information available on this? I seem to have hit some pathological worst-case behavior with very cpu-heavy tasks, where every thread except one ended up totally stalled. Disabling the LIFO slot resolved the problem, giving me a 20x speedup.

@Darksonn
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Darksonn commented Sep 4, 2023

It has not been implemented yet.

@Darksonn Darksonn mentioned this issue Feb 1, 2024
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@carllerche @Darksonn @MortenLohne