Periodic Stutters on some Mac hardware

Bevy version

The problem is on both:

0.6.0
The current main branch (3fcdc5a at the moment)

Bevy 0.5.0 did not exhibit this problem.

If I add the plugins from either of the projects below, then I get periodic stuttering / dropped frames. I'm speculating this has something to do with the big rendering overhaul plus these plugins using custom shaders (?).

bevy_prototype_debug_lines
bevy_prototype_lyon

Note: I don't have to use the plugins to see the problem (though I do use them in the code provided)! Just adding the plugin app.add_plugin( ... ) is enough to trigger the problem in my testing.

Operating system & version

Here's the specs for my workstation with the problem.

$ rustc --version
rustc 1.58.0 (02072b482 2022-01-11)

I also tried Rust 1.57 -- no change. I've run cargo update to make sure I'm using the latest crates.io dependencies -- no change.

NOTE: This very similar system does NOT show the problem, or at least I can't reproduce it. I don't know whether the difference is the OS revision, the specific hardware, or something else.

What you did

$ git clone https://github.com/CleanCut/rusty_engine.git
$ cd rusty_engine
$ git checkout choppy
$ cargo run --release --example road_race

# Use the arrow keys to avoid obstacles, just so the game proceeds long enough to observe
# the periodic stutters on some hardware. In my experience, every 0.25 to 5 seconds there
# will be a stutter. The length of the stutter is variable--I've observed stutter durations of
# maybe a single frame to nearly a full second (my guesstimate -- I don't know how to
# measure it!).

# Compare to...

$ git checkout smooth -- Update: no stutters on my Intel boxen, still stutters on my M1 & @mockersf's M1 Max
$ cargo run --release --example road_race

What you expected to happen

No stutters.

What actually happened

Stutters.

Additional information

I originally thought this was a bug in bevy_prototype_debug_lines, so I filed an issue with that project.

There are 5 tags/branches in the CleanCut/rusty_engine repository you can check out if you like. They're all exhibit the stutter for me except the first one:

The smooth tag uses neither plugin - Update: Though this didn't stutter on my Intel machines, we discovered it still stutters on Apple M1 and M1 Max machines.
The choppy tag is bevy_prototype_debug_lines with Bevy 0.6.0
The bevy-main-debug-lines branch is bevy_prototype_debug_lines with Bevy main
The choppy-lyon tag is bevy_prototype_lyon with Bevy 0.6.0
The bevy-main-lyon branch is bevy_prototype_lyon with Bevy main

If you prefer an example where you don't have to dodge obstacles, you can run:

cargo run --release --example collision
(optional) Press the C key to turn on the debug lines (it doesn't make a difference, but the debug lines are what I'm trying to implement nicely)
Hold down the left mouse button to rotate the sprite -- then just wait for stutters.

I tried running branches choppy and smooth on my mac (macOS Monterey 12.1, m1 max) and both run the same for me... they both stutter

Whoah! smooth didn't stutter for me on Intel Montery 12.1 (hence the name). 🤔 Do you normally get stutter with Bevy 0.6? Is there something I can do to help narrow down the issue? Maybe try out that "tracy" profiler? I know little to nothing about the guts of rendering, but I'm more than willing to do some legwork if it'll help.

I've got access to a first-gen M1 -- I can try that as well for another data point.

I confirmed that I see stutter on all five branches I mentioned on an M1 (including the smooth branch). I guess it's just the current state of the new renderer?

I enabled the bevy "trace_tracy" and ran road_race from the "choppy" branch. (2021 m1 mac)

Tracy lets you sort all "frame" spans by execution time. One particular long (34ms) frame looked like this:

With the full name of that bottom-most "RenderDevice" span being:

system{�[3mname�[0m�[2m=�[0m"(bevy_ecs::change_detection::ResMut<bevy_render::render_asset::ExtractedAssets<bevy_render::mesh::mesh::Mesh>>, bevy_ecs::change_detection::ResMut<std::collections::hash::map::HashMap<bevy_asset::handle::Handle<bevy_render::mesh::mesh::Mesh>, bevy_render::mesh::mesh::GpuMesh, ahash::random_state::RandomState>>, bevy_ecs::change_detection::ResMut<bevy_render::render_asset::PrepareNextFrameAssets<bevy_render::mesh::mesh::Mesh>>, bevy_ecs::system::system_param::Res<bevy_render::renderer::render_device::RenderDevice>)"}

And lasting 24ms.

I don't really know how to interpret this.

That particular long frame was captured some number of nanoseconds after startup, so maybe that's not interesting. Here's another "long frame" from 9 seconds into play:

where there seems to be a lot of action in the PostUpdate stage, but not in a named span.

@rparrett

@rparrett Is there a doc somewhere that I can read to learn how to get set up with the tracing stuff? The 0.6 news post just mentions the trace_tracy feature and links to https://github.com/wolfpld/tracy - I'm having trouble figuring out how to get/build/run tracy to get the profile. I skimmed through the whole tracy PDF user guide...and it's not helping with the "get started" stuff.

Update: Naturally, right after I ask the question I finally figure out the building step. Sort of. There are hints at the bottom of page 18 in the PDF user manual (sheesh, talk about buried -- put it on the readme, folks -- or better yet add it to homebrew).

Here's what I did to build the tracy profiler on macOS:

# (I've done this on macOS 11.6.2 Big Sur Intel -- I'll try other OS/hardware combinations later)

$ brew install pkg-config glfw freetype capstone gtk+3
# (clone the wolfpld/tracy repo and `cd` into it)
$ git checkout v0.7.8
$ cd profiler/build/unix
$ make release

# I copy `Tracy-release` to `tracy` somewhere in my PATH, but you can do what you want

This builds a binary called Tracy-release in that profiler/build/unix directory. Running it opens a UI.

Then I added the trace_tracy feature to bevy in my Cargo.toml and rebuilt it. The OS prompted me whether I wanted to accept incoming network connections, I OK'd it (twice--once for the bevy app, once for the tracy profiler app).

~~The tracy profiler UI auto-detects the presence of my running program, but when I mouse over to connect to it a box pops up with the error: Incompatible Protocol! (used: 46, required: 55)~~ Building on tag v0.7.8 fixes that.

Then you click on the line with your program's name (road_race in this screenshot) and it connects!

Yeah, no kidding. It's not too bad though:

https://dev.to/stein/build-the-tracy-profiler-server-on-macos-36k6
enable the trace_tracy feature on your bevy dependency
run the profiler and click connect
run your app

But if anyone has any tips for actually using Tracy well with a touchpad, I'm all ears.

Thanks! Now I've just got to figure out which older version of Tracy corresponds to "protocol version 46"

I'm using tracy tag v0.7.8 to build locally and it works with Bevy

But if anyone has any tips for actually using Tracy well with a touchpad, I'm all ears.

Have a very steady hand when scrolling horizontally

I'm using tracy tag v0.7.8 to build locally and it works with Bevy

Thanks! I updated my instructions above.

Now my challenge will be to learn how to use this thing. I get the feeling that this will be a valuable skill in my future life using Bevy.

Maybe I can find some helpful info to add to this issue tonight.

Any tips on how best to use the Tracy Profiler UI?

Last night I profiled on the M1 for about 20 minutes. Ironically, it ran much more smoothly with the tracing enabled. At the end I figured out how to use the search to identify the longest frame, which was only ~42ms. 🤷🏻‍♂️ I need to try it on the Intel box.

Just enabling the trace_tracy feature on both my M1 and Intel boxes decreases the amount of stutter by quite a bit, but it does still occasionally occur. Here's the dump of a quick trace I did. About 11s in a frame took 34ms. Does this shed any light on the subject for anyone? It appears suspiciously like the threads in green and/or yellow are the culprits, but I really don't have any clue how Bevy's (or wgpu's) rendering works. The names on those bars are:

(green) bevy_render::render_component::prepare_uniform_components<bevy_sprite::mesh2d::mesh::Mesh2dUniform>
(yellow) bevy_ecs::change_detection::ResMut<bevy_render::render_asset::ExtractedAssets<bevy_render::mesh::mesh::Mesh>>, bevy_ecs::change_detection::ResMut<std::collections::hash::map::HashMap<bevy_asset::handle::Handle<bevy_render::mesh::mesh::Mesh>, bevy_render::mesh::mesh::GpuMesh, ahash::random_state::RandomState>>, bevy_ecs::change_detection::ResMut<bevy_render::render_asset::PrepareNextFrameAssets<bevy_render::mesh::mesh... (I can't find a way to get the rest of it)

If you zoom out a bit, you'll notice that those two threads are not active with those two items at the same time in any of the well-timed frames:

I have no idea where to go from here.

I don't think this is something Mac-specific: Toqozz/bevy_debug_lines#14 (comment)

Resolved in Bevy 0.8

@CleanCut

@CleanCut which PR is the fix for this?

Most likely #4744

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Periodic Stutters on some Mac hardware #3709

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Periodic Stutters on some Mac hardware #3709

Description

Bevy version

Operating system & version

What you did

What you expected to happen

What actually happened

Additional information

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mockersf commented on Jan 17, 2022

CleanCut commented on Jan 17, 2022

CleanCut commented on Jan 18, 2022

rparrett commented on Jan 18, 2022

rparrett commented on Jan 18, 2022

CleanCut commented on Jan 18, 2022

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CleanCut commented on Jan 18, 2022

mockersf commented on Jan 18, 2022

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rparrett commented on Aug 2, 2022

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