Usage with only compute shaders

[NyxCode]

Hey!
I've got roughly this setup:

let mut encoder = device.create_command_encoder(&Default::default());
{
    let mut encoder = profiler.scope("radix sort", &mut encoder);
    for i in 0..8 {
        {
            let mut encoder = encoder.scope("histogram");
            let mut pass = encoder.begin_compute_pass(&Default::default());
            // ...
            pass.dispatch_workgroups(x, y, z);
       }
        {
            let mut encoder = encoder.scope("prefix sum");
            let mut pass = encoder.begin_compute_pass(&Default::default());
            // ...
            pass.dispatch_workgroups(x, y, z);
       }
       // ...
    }
}
profiler.resolve_queries(&mut encoder);
let command_buffer = encoder.finish();
queue.submit([command_buffer]);

profiler.end_frame().unwrap();
device.poll(wgpu::wgt::PollType::Wait { submission_index: None, timeout: None }).unwrap();
let results = profiler.process_finished_frame(queue.get_timestamp_period()).unwrap();

The results I get back contain entries for all created scopes (the top-level one, and 3 for each iteration, so 25 in total).
However, most of the time, all of them have a recorded time of Some(0.0..0.0). All zeros everywhere.
Sometimes, I do get some results back, but always without the last 3 iterations (3 scopes each) - those are present in the results, but again with 0s as timings. What am I doing wrong here?

Running on Adapter: AdapterInfo {
    name: "AMD Radeon RX 5700 XT",
    vendor: 4098,
    device: 29471,
    device_type: DiscreteGpu,
    driver: "AMD proprietary driver",
    driver_info: "25.9.1 (AMD proprietary shader compiler)",
    backend: Vulkan,
}

using wgpu v27 and the latest master commit of wgpu-profiler

[NyxCode]

Huh, now I've had one run where only the last 9 scopes have timings. Something's definitely off 😄

[NyxCode]

Okay, it seems like the wgpu vulkan backend is the culprit. This just works with the DX12 backend.

[Wumpf]

Yeah I think you're running into

• Vulkan timestamp queries can return 0 if resolved too soon gfx-rs/wgpu#6406
• Timestamps are wrong on Vulkan #84

[nazar-pc]

Thank you for this example!

The documentation in readme is written for someone who already knows what they are doing. I was calling profiler.end_frame().unwrap(); before polling the device and was not getting anything out of process_finished_frame() and had no idea why. Now I do get at least something.