1880415 - https://webgpu.github.io/webgpu-samples/samples/imageBlur takes a long time to compile shaders

Status: RESOLVED FIXED

(Core :: Graphics: WebGPU, defect)

Description

[Mayank Bansal]

Go to https://webgpu.github.io/webgpu-samples/samples/imageBlur

AR: https://share.firefox.dev/3urFgJY (profile wihtWebgpu preset logging)

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[Mayank Bansal]

This happens with/without dx12-no-readback , and with all 3 canvas backends (d2d, gpu, skia)

Comment 3

[Erich Gubler [:ErichDonGubler] (he/him)]

I'm going to change the scope of this bug to include whatever is needed to make this specific page work, since AFAIK nothing is tracking it yet. There's at least two issues at play here:

• Shader compilation (specifically, D3D's optimization passes over shader code) appears to be the source of the hang/freeze—at least on Windows—with the vast majority of the paused time being in third_party/rust/wgpu-hal/src/dx12/shader_compilation.rs:38's call to D3DCompile. This takes ~15 seconds on my personal workstation. Nuts!
• I also see some shaders failing on bug 1878320.

Linking against 1806659, which serves as a meta-bug for WebGPU's official samples.

Comment 4

[Erich Gubler [:ErichDonGubler] (he/him)]

Aha, perf. issues are definitely the newly filed bug 1885217. 😭👍🏻

Comment 5

[Erich Gubler [:ErichDonGubler] (he/him)]

Bug 1878449, comment 5 is applicable here; perf. issues are fundamental to any shader compilation that is long (which even the best shader compiler might not be able to prevent). The solution is offered by the spec. in the form of GPUDevice.createComputePipelineAsync.

Comment 6

[Erich Gubler [:ErichDonGubler] (he/him)]

With recent fixes in WebGPU, this page now successfully loads for me, but the long shader compilation delay is still present because we're using FXC for compilation.

Comment 7

[Mayank Bansal]

Latest profile: https://share.firefox.dev/42xPfft
Working as expected.