[Windows][Concurrency] Use the same clock as Dispatch. #76310
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The Concurrency runtime calculates deadlines for scheduling itself using `swift_get_time()`; unfortunately, on Windows that was using `QueryPerformanceCounter()`, while Dispatch uses `QueryInterruptTimePrecise()`. The problem with that is that the two do not necessarily correspond *at all*. In general `QueryPerformanceCounter()` may be using any of a number of hardware timers depending on the machine on which we're running. In the VM I was testing on, the two differed by 20ms, but the worst case is that they are completely unrelated, in which case `Task.sleep()` will wait essentially a random amount of time. rdar://135413803
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| @swift-ci Please test |
compnerd approved these changes Sep 6, 2024
grynspan reviewed Sep 6, 2024
grynspan requested changes Sep 6, 2024
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grynspan left a comment
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You also need to update swift_get_clock_res().
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Nice spot. You're right, I do. |
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Fortunately, you can just use the exact same code as for the other clock. :) |
I should have updated this to match as well. rdar://135413803
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| @swift-ci Please test |
Since we're linking `mincore.lib`, we don't need to use `GetProcAddress()` to find `Query[Unbiased]InterruptTimePrecise()`. rdar://135413803
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| @swift-ci Please test |
grynspan reviewed Sep 6, 2024
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| Related: #63225 |
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The Concurrency runtime calculates deadlines for scheduling itself using
swift_get_time(); unfortunately, on Windows that was usingQueryPerformanceCounter(), while Dispatch usesQueryInterruptTimePrecise(). The problem with that is that the two do not necessarily correspond at all. In generalQueryPerformanceCounter()may be using any of a number of hardware timers depending on the machine on which we're running.In the VM I was testing on, the two differed by 20ms, but the worst case is that they are completely unrelated, in which case
Task.sleep()will wait essentially a random amount of time.Fixes #72095.
rdar://135413803