unix,win: fix busy loop with zero timeout timers#4250
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bnoordhuis merged 3 commits intolibuv:v1.xfrom Dec 22, 2023
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vtjnash
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Without fully reviewing the implementation, this approach SGTM
bnoordhuis
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Can you check how this affects the million_timers benchmark?
As a possible improvement: instead of a flag, always uv__queue_init() when the handle is stopped. That simplifies the uv_timer_stop() logic to:
if (uv__is_active(handle)) {
heap_remove(timer_heap(handle->loop), &handle->u.heap_node, timer_less_than);
uv__handle_stop(handle);
} else {
uv__queue_remove(&handle->u.queue_node);
}
uv__queue_init(&handle->u.queue_node);With complementary logic in uv_timer_start().
Calling `uv_timer_start(h, cb, 0, 0)` from a timer callback resulted in the timer running immediately because it was inserted at the front of the timer heap. If the callback did that every time, libuv would effectively busy-loop in `uv__run_timers()` and never make forward progress. Work around that by collecting all expired timers into a queue and only running their callback afterwards. Fixes: libuv#4245
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For that benchmark, there is essentially no difference. Follows sample output for one run, and average of 10 runs computed with hyperfine: Old: New: Tests run on Windows 11 system with |
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Thanks Matheus, merged. |
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santigimeno
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Feb 6, 2024
This reverts commit 51a22f6.
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Calling
uv_timer_start(h, cb, 0, 0)from a timer callback resulted inthe timer running immediately because it was inserted at the front of
the timer heap.
If the callback did that every time, libuv would effectively busy-loop
in
uv__run_timers()and never make forward progress.Work around that by collecting all expired timers into a queue and only
running their callback afterwards.
Fixes: #4245