fab83471b5
3 Commits
| Author | SHA1 | Message | Date | |
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James Liu
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ae9775c83b
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Optimize Event Updates (#12936)
# Objective Improve performance scalability when adding new event types to a Bevy app. Currently, just using Bevy in the default configuration, all apps spend upwards of 100+us in the `First` schedule, every app tick, evaluating if it should update events or not, even if events are not being used for that particular frame, and this scales with the number of Events registered in the app. ## Solution As `Events::update` is guaranteed `O(1)` by just checking if a resource's value, swapping two Vecs, and then clearing one of them, the actual cost of running `event_update_system` is *very* cheap. The overhead of doing system dependency injection, task scheduling ,and the multithreaded executor outweighs the cost of running the system by a large margin. Create an `EventRegistry` resource that keeps a number of function pointers that update each event. Replace the per-event type `event_update_system` with a singular exclusive system uses the `EventRegistry` to update all events instead. Update `SubApp::add_event` to use `EventRegistry` instead. ## Performance This speeds reduces the cost of the `First` schedule in both many_foxes and many_cubes by over 80%. Note this is with system spans on. The majority of this is now context-switching costs from launching `time_system`, which should be mostly eliminated with #12869.  The actual `event_update_system` is usually *very* short, using only a few microseconds on average.  --- ## Changelog TODO ## Migration Guide TODO --------- Co-authored-by: Josh Matthews <josh@joshmatthews.net> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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Carter Anderson
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a042924a6e
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Time: demote delta time clamping warning to debug (#10145)
# Objective Time clamping happens consistently for apps that load non-trivial things. While this _is_ an indicator that we should probably try to move this work to a thread that doesn't block the Update, this is common enough (and unactionable enough) that I think we should demote it for now. ``` 2023-10-16T18:46:14.918781Z WARN bevy_time::virt: delta time larger than maximum delta, clamping delta to 250ms and skipping 63.649253ms 2023-10-16T18:46:15.178048Z WARN bevy_time::virt: delta time larger than maximum delta, clamping delta to 250ms and skipping 1.71611ms ``` ## Solution Change `warn` to `debug` for this message |
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Nuutti Kotivuori
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3d79dc4cdc
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Unify FixedTime and Time while fixing several problems (#8964)
# Objective Current `FixedTime` and `Time` have several problems. This pull aims to fix many of them at once. - If there is a longer pause between app updates, time will jump forward a lot at once and fixed time will iterate on `FixedUpdate` for a large number of steps. If the pause is merely seconds, then this will just mean jerkiness and possible unexpected behaviour in gameplay. If the pause is hours/days as with OS suspend, the game will appear to freeze until it has caught up with real time. - If calculating a fixed step takes longer than specified fixed step period, the game will enter a death spiral where rendering each frame takes longer and longer due to more and more fixed step updates being run per frame and the game appears to freeze. - There is no way to see current fixed step elapsed time inside fixed steps. In order to track this, the game designer needs to add a custom system inside `FixedUpdate` that calculates elapsed or step count in a resource. - Access to delta time inside fixed step is `FixedStep::period` rather than `Time::delta`. This, coupled with the issue that `Time::elapsed` isn't available at all for fixed steps, makes it that time requiring systems are either implemented to be run in `FixedUpdate` or `Update`, but rarely work in both. - Fixes #8800 - Fixes #8543 - Fixes #7439 - Fixes #5692 ## Solution - Create a generic `Time<T>` clock that has no processing logic but which can be instantiated for multiple usages. This is also exposed for users to add custom clocks. - Create three standard clocks, `Time<Real>`, `Time<Virtual>` and `Time<Fixed>`, all of which contain their individual logic. - Create one "default" clock, which is just `Time` (or `Time<()>`), which will be overwritten from `Time<Virtual>` on each update, and `Time<Fixed>` inside `FixedUpdate` schedule. This way systems that do not care specifically which time they track can work both in `Update` and `FixedUpdate` without changes and the behaviour is intuitive. - Add `max_delta` to virtual time update, which limits how much can be added to virtual time by a single update. This fixes both the behaviour after a long freeze, and also the death spiral by limiting how many fixed timestep iterations there can be per update. Possible future work could be adding `max_accumulator` to add a sort of "leaky bucket" time processing to possibly smooth out jumps in time while keeping frame rate stable. - Many minor tweaks and clarifications to the time functions and their documentation. ## Changelog - `Time::raw_delta()`, `Time::raw_elapsed()` and related methods are moved to `Time<Real>::delta()` and `Time<Real>::elapsed()` and now match `Time` API - `FixedTime` is now `Time<Fixed>` and matches `Time` API. - `Time<Fixed>` default timestep is now 64 Hz, or 15625 microseconds. - `Time` inside `FixedUpdate` now reflects fixed timestep time, making systems portable between `Update ` and `FixedUpdate`. - `Time::pause()`, `Time::set_relative_speed()` and related methods must now be called as `Time<Virtual>::pause()` etc. - There is a new `max_delta` setting in `Time<Virtual>` that limits how much the clock can jump by a single update. The default value is 0.25 seconds. - Removed `on_fixed_timer()` condition as `on_timer()` does the right thing inside `FixedUpdate` now. ## Migration Guide - Change all `Res<Time>` instances that access `raw_delta()`, `raw_elapsed()` and related methods to `Res<Time<Real>>` and `delta()`, `elapsed()`, etc. - Change access to `period` from `Res<FixedTime>` to `Res<Time<Fixed>>` and use `delta()`. - The default timestep has been changed from 60 Hz to 64 Hz. If you wish to restore the old behaviour, use `app.insert_resource(Time::<Fixed>::from_hz(60.0))`. - Change `app.insert_resource(FixedTime::new(duration))` to `app.insert_resource(Time::<Fixed>::from_duration(duration))` - Change `app.insert_resource(FixedTime::new_from_secs(secs))` to `app.insert_resource(Time::<Fixed>::from_seconds(secs))` - Change `system.on_fixed_timer(duration)` to `system.on_timer(duration)`. Timers in systems placed in `FixedUpdate` schedule automatically use the fixed time clock. - Change `ResMut<Time>` calls to `pause()`, `is_paused()`, `set_relative_speed()` and related methods to `ResMut<Time<Virtual>>` calls. The API is the same, with the exception that `relative_speed()` will return the actual last ste relative speed, while `effective_relative_speed()` returns 0.0 if the time is paused and corresponds to the speed that was set when the update for the current frame started. ## Todo - [x] Update pull name and description - [x] Top level documentation on usage - [x] Fix examples - [x] Decide on default `max_delta` value - [x] Decide naming of the three clocks: is `Real`, `Virtual`, `Fixed` good? - [x] Decide if the three clock inner structures should be in prelude - [x] Decide on best way to configure values at startup: is manually inserting a new clock instance okay, or should there be config struct separately? - [x] Fix links in docs - [x] Decide what should be public and what not - [x] Decide how `wrap_period` should be handled when it is changed - [x] ~~Add toggles to disable setting the clock as default?~~ No, separate pull if needed. - [x] Add tests - [x] Reformat, ensure adheres to conventions etc. - [x] Build documentation and see that it looks correct ## Contributors Huge thanks to @alice-i-cecile and @maniwani while building this pull. It was a shared effort! --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Cameron <51241057+maniwani@users.noreply.github.com> Co-authored-by: Jerome Humbert <djeedai@gmail.com> |