bevy/crates/bevy_render
Mike 6b84ba97a3
Auto insert sync points (#9822)
# Objective

- Users are often confused when their command effects are not visible in
the next system. This PR auto inserts sync points if there are deferred
buffers on a system and there are dependents on that system (systems
with after relationships).
- Manual sync points can lead to users adding more than needed and it's
hard for the user to have a global understanding of their system graph
to know which sync points can be merged. However we can easily calculate
which sync points can be merged automatically.

## Solution

1. Add new edge types to allow opting out of new behavior
2. Insert an sync point for each edge whose initial node has deferred
system params.
3. Reuse nodes if they're at the number of sync points away.

* add opt outs for specific edges with `after_ignore_deferred`,
`before_ignore_deferred` and `chain_ignore_deferred`. The
`auto_insert_apply_deferred` boolean on `ScheduleBuildSettings` can be
set to false to opt out for the whole schedule.

## Perf
This has a small negative effect on schedule build times.
```text
group                                           auto-sync                              main-for-auto-sync
-----                                           -----------                            ------------------
build_schedule/1000_schedule                    1.06       2.8±0.15s        ? ?/sec    1.00       2.7±0.06s        ? ?/sec
build_schedule/1000_schedule_noconstraints      1.01     26.2±0.88ms        ? ?/sec    1.00     25.8±0.36ms        ? ?/sec
build_schedule/100_schedule                     1.02     13.1±0.33ms        ? ?/sec    1.00     12.9±0.28ms        ? ?/sec
build_schedule/100_schedule_noconstraints       1.08   505.3±29.30µs        ? ?/sec    1.00   469.4±12.48µs        ? ?/sec
build_schedule/500_schedule                     1.00    485.5±6.29ms        ? ?/sec    1.00    485.5±9.80ms        ? ?/sec
build_schedule/500_schedule_noconstraints       1.00      6.8±0.10ms        ? ?/sec    1.02      6.9±0.16ms        ? ?/sec
```
---

## Changelog

- Auto insert sync points and added `after_ignore_deferred`,
`before_ignore_deferred`, `chain_no_deferred` and
`auto_insert_apply_deferred` APIs to opt out of this behavior

## Migration Guide

- `apply_deferred` points are added automatically when there is ordering
relationship with a system that has deferred parameters like `Commands`.
If you want to opt out of this you can switch from `after`, `before`,
and `chain` to the corresponding `ignore_deferred` API,
`after_ignore_deferred`, `before_ignore_deferred` or
`chain_ignore_deferred` for your system/set ordering.
- You can also set `ScheduleBuildSettings::auto_insert_sync_points` to
`false` if you want to do it for the whole schedule. Note that in this
mode you can still add `apply_deferred` points manually.
- For most manual insertions of `apply_deferred` you should remove them
as they cannot be merged with the automatically inserted points and
might reduce parallelizability of the system graph.

## TODO
- [x] remove any apply_deferred used in the engine
- [x] ~~decide if we should deprecate manually using apply_deferred.~~
We'll still allow inserting manual sync points for now for whatever edge
cases users might have.
- [x] Update migration guide
- [x] rerun schedule build benchmarks

---------

Co-authored-by: Joseph <21144246+JoJoJet@users.noreply.github.com>
2023-12-14 16:34:01 +00:00
..
macros Rename WorldQueryData & WorldQueryFilter to QueryData & QueryFilter (#10779) 2023-12-12 19:45:50 +00:00
src Auto insert sync points (#9822) 2023-12-14 16:34:01 +00:00
Cargo.toml Update to wgpu 0.18 (#10266) 2023-12-14 02:45:47 +00:00