~22-25 ms hitches: vk_syncBegin stalls 7-8 ms alongside texture-upload spikes #535

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opened 2026-10-08 04:50:11 +00:00 by sky_line · 0 comments

sky_line commented

2026-10-08 04:50:11 +00:00

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Observed (same session as the 10 s sweep hitch): occasional hitch frames of 22-25 ms. Each shows:

renderFrame 13-15 ms;
vk_syncBegin 7-8 ms (the steady-state average is 0.03 ms);
usually vk_texUpload / vk_syncFromStores around 3 ms and vk_texResidency around 2.5 ms in the same frame.

Likely cause: something at the start of the render-side frame sync waits on, or processes, a large batch. Candidates: texture upload or residency batches, staging-buffer recycling, or a fence wait.

Done when:

we can say what vk_syncBegin waits on during these frames;
that work is moved off the frame, budgeted, or made asynchronous;
there are no more 7 ms vk_syncBegin spikes in the VKHitch log in the same scene.

**Observed** (same session as the 10 s sweep hitch): occasional hitch frames of 22-25 ms. Each shows: - `renderFrame` 13-15 ms; - `vk_syncBegin` 7-8 ms (the steady-state average is 0.03 ms); - usually `vk_texUpload` / `vk_syncFromStores` around 3 ms and `vk_texResidency` around 2.5 ms in the same frame. **Likely cause:** something at the start of the render-side frame sync waits on, or processes, a large batch. Candidates: texture upload or residency batches, staging-buffer recycling, or a fence wait. **Done when:** - we can say what vk_syncBegin waits on during these frames; - that work is moved off the frame, budgeted, or made asynchronous; - there are no more 7 ms vk_syncBegin spikes in the VKHitch log in the same scene.

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