macOS: BufferUsage::all() breaks examples

[colinmarc]

Running the triangle example on a fresh install of macOS with the vulkan SDK, I get a blue screen but no triangles:

My laptop is a 2020 macbook air, still with the new computer smell, and an integrated GPU.

I'm more than happy to debug myself, given some direction! I'm not really sure where to start.

[colinmarc]

Also, just running the simplest example from the guide:

let source_content = 0..64;
let source =
    CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), false, source_content)
        .expect("failed to create buffer");

let dest_content = (0..64).map(|_| 0_i32);
let dest =
    CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), false, dest_content)
        .expect("failed to create buffer");

let mut builder = AutoCommandBufferBuilder::new(device.clone(), queue.family()).unwrap();
builder.copy_buffer(source.clone(), dest.clone()).unwrap();
let command_buffer = builder.build().unwrap();

command_buffer
    .execute(queue.clone())
    .unwrap()
    .then_signal_fence_and_flush()
    .unwrap()
    .wait(None)
    .unwrap();

let src_content = source.read().unwrap();
let dest_content = dest.read().unwrap();
assert_eq!(&*src_content, &*dest_content);

It doesn't seem to actually do the thing.

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]`,
 right: `[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]`', src/main.rs:63:5

[AustinJ235]

Related: #1368 (comment)

Cause is still unknown at this time. I don't have access to macOS hardware either. You could try using previous versions of the macOS deps here:

vulkano/vulkano-win/Cargo.toml

Line 24 in c5dd6ed

[target.'cfg(target_os = "macos")'.dependencies]

Maybe using another queue from the returned queue families? Maybe try broadening the ImageUsage on the Swapchain:

vulkano/examples/src/bin/triangle.rs

Line 182 in c5dd6ed

ImageUsage::color_attachment(),

Not sure anything seems to be possible. If there a debugging tools available you could try to find one and see if it gives any errors or warnings.

[colinmarc]

Sorry for spamming! Hopefully my debugging process is useful to someone.

I got git bisect working with DYLD_LIBRARY_PATH="$HOME/src/MoltenVK/Package/Release/MoltenVK/macOS/dynamic:$VULKAN_SDK/lib:${DYLD_LIBRARY_PATH:-}", and I've isolated the issue to commit 25a1e056 in MoltenVK.

It looks like the issue is something with BufferUsage::all(). When I change the way the buffers are created in the memory copy example from

let source = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), false, source_content)?;
let dest = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), false, dest_content)?;

to

let source = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::transfer_source(), false, source_content)?;
let dest = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::transfer_dest(), false, dest_content)?;

Then it suddenly works. Similarly, changing the code in the triangle example to use BufferUsage::vertex_buffer() works, too.

My question: should I make a PR to change the examples or is this a bug in BufferUsage::all?

[AustinJ235]

Certainly wondering if there was a change in spec or something that changed how usages work. In practice having a broad usage shouldn't cause issues, it may just be nonoptimal. Changing the guide to further explain usages instead of using BufferUsage::all() everywhere would probably be a good idea and all the examples also.

As to why this is causing poor behaviour I note quite sure.

[Xazzzi]

I have same behaviour on mid 2015 mac pro, tweaking BufferUsage worked.
For me simplest example - filling cpu accessible buffer with constant - stops working when either of usage flags are set:

uniform_texel_buffer: true,
storage_texel_buffer: true,

Which seems related to the commmit @colinmarc pointed to.

[stetrevor]

For me,it worked after I changed the host_cached argument from false to true in all CpuAccessibleBuffer​::​from_iter calls. Both the buffer copy example and the triangle example work now.

From:

let​ source ​=​ CpuAccessibleBuffer​::​from_iter​(device.​clone​(), BufferUsage​::​transfer_source​(), ​false, source_content)?;

To:

let​ source ​=​ CpuAccessibleBuffer​::​from_iter​(device.​clone​(), BufferUsage​::​transfer_source​(), ​true, source_content)?;