Timer refactoring #2905
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Timer refactoring #2905
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Darksonn
added
A-tokio
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Relevant: #2897 |
carllerche
approved these changes
Oct 5, 2020
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LGTM 👍. A solid cleanup.
There will be merge conflicts w/ #2897, but hopefully, it shouldn't be too bad.
the timer wheel uses the `wheel::Poll` struct as input when advancing the timer to the next time step. the `Poll` struct contains an instant representing the time step to advance to and also contains an optional and mutable reference to an `Expiration` struct. from what I can tell, the latter field is only used in the context of polling the wheel and does not need to be exposed outside of that method. without the expiration field the `Poll` struct is nothing more than a wrapper around the instant being polled. this change removes the `Poll` struct and updates integration points accordingly.
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Rebased onto #2897 , no functional changes |
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Motivation
I've been talking to @carllerche over the last few weeks about simplifying the implementation of the timer and delay implementation within the existing interface. This is the first stab at that refactor.
Solution
Changes included in this PR:
wheel::Pollstruct. it appears to be a pretty thin wrapper aroundu64that provides limited functionality/valuedelay_queuemodule completely. in chatting with @carllerche it sounds like we're planning on moving that totokio-utilanywaysdelay_queueis removed, we don't need the generic behavior that allows the timer wheel to operate on both a slab and stack state directly - the only concrete store used is the stack directly. so now that it is removed we can make the timer wheel non-generic.Registrationstruct, which appears to be a fairly thin wrapper around theEntrystruct with limited functionality/value.This is my first foray into the tokio ecosystem, so it's very likely that I'm missing the motivation around why things are the way they currently are - very open to suggestions and corrections. I also view this as the first in a few different efforts to rework the timer implementation. My next area of focus will be to reduce the amount of state that is shared across the
Entrystruct, which is the point of synchronization between the timer driver and theDelayitself. Reducing the surface area ofEntrywill probably make the delay implementation slimmer and easier to reason about. I'm open to suggestions on that future work as well.