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Pin an Executor's State to minimize atomic operations.#146

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james7132 merged 5 commits intosmol-rs:masterfrom
james7132:pinned-state
Aug 27, 2025
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Pin an Executor's State to minimize atomic operations.#146
james7132 merged 5 commits intosmol-rs:masterfrom
james7132:pinned-state

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@james7132 james7132 commented Aug 14, 2025

Use Pin<&'a State> to point to the state instead of cloning Arcs, this should reduce the amount of atomic operations required.

This should be sound given that the state are never moved until the Executor is dropped. This still uses Arc instead of Box as miri will treat a former Box as a uniquely owned pointer and cannot be shared (backed by Unique vs Shared).

Benchmark results:

group                                               master                                 pinned-state
-----                                               ------                                 ------------
executor::create                                    1.06  944.7±129.72ns        ? ?/sec    1.00   889.7±17.24ns        ? ?/sec
multi_thread/executor::channels                     1.00     35.5±0.76ms        ? ?/sec    1.00     35.7±0.75ms        ? ?/sec
multi_thread/executor::spawn_batch                  1.23     27.8±5.06µs        ? ?/sec    1.00     22.6±9.96µs        ? ?/sec
multi_thread/executor::spawn_many_local             1.08     23.2±0.57ms        ? ?/sec    1.00     21.5±0.79ms        ? ?/sec
multi_thread/executor::spawn_one                    1.07   995.0±35.82ns        ? ?/sec    1.00   929.5±26.16ns        ? ?/sec
multi_thread/executor::spawn_recursively            1.06    144.8±1.28ms        ? ?/sec    1.00    136.8±1.56ms        ? ?/sec
multi_thread/executor::web_server                   1.00     50.9±1.03ms        ? ?/sec    1.00     51.1±1.80ms        ? ?/sec
multi_thread/executor::yield_now                    1.00     20.2±0.61ms        ? ?/sec    1.01     20.4±0.28ms        ? ?/sec
single_thread/executor::channels                    1.00     14.4±0.41ms        ? ?/sec    1.07     15.4±0.66ms        ? ?/sec
single_thread/executor::spawn_batch                 1.08    20.2±11.74µs        ? ?/sec    1.00     18.7±8.31µs        ? ?/sec
single_thread/executor::spawn_many_local            1.11      5.4±0.72ms        ? ?/sec    1.00      4.9±0.24ms        ? ?/sec
single_thread/executor::spawn_one                   1.02  1422.7±75.41ns        ? ?/sec    1.00  1388.6±42.78ns        ? ?/sec
single_thread/executor::spawn_recursively           1.03     22.6±1.05ms        ? ?/sec    1.00     21.9±1.11ms        ? ?/sec
single_thread/executor::web_server                  1.03     23.0±0.22ms        ? ?/sec    1.00     22.3±0.31ms        ? ?/sec
single_thread/executor::yield_now                   1.02      4.1±0.06ms        ? ?/sec    1.00      4.0±0.03ms        ? ?/sec

@james7132 james7132 requested a review from notgull August 14, 2025 01:42
@james7132 james7132 mentioned this pull request Aug 14, 2025
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notgull commented Aug 16, 2025

I intend to review this, but I am preoccupied at the moment.

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notgull requested changes Aug 24, 2025
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Overall looks good, one minor nitpick.

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notgull approved these changes Aug 27, 2025
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Thanks! Rebase and I will merge. (Or you can too.)

@james7132 james7132 merged commit c10412c into smol-rs:master Aug 27, 2025
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@taiki-e taiki-e mentioned this pull request Jan 20, 2026
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