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[Performance] Severe CPU-side rendering bottleneck in Kokiri Forest (21–42 FPS, low GPU usage) #410

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opened 2026-11-14 10:45:52 +00:00 by LeFaxen · 0 comments

LeFaxen commented

2026-11-14 10:45:52 +00:00

Longshot version

longshot nightly-130-0caf0618

Channel

Release candidate

What kind of problem

Low fps or stutter

What happened

I'm experiencing significant performance issues in Kokiri Forest, particularly when looking across the village from certain viewpoints.

My system is a Shadow Power Pro cloud PC with a virtualized AMD EPYC 7543P CPU (4 physical cores / 8 logical processors), an NVIDIA RTX A4500 20 GB GPU, and 28 GB RAM.

At 1920x1080 output resolution, performance usually ranges between 30 and 42 FPS, but drops to approximately 21–24 FPS when looking across the village. This issue is reproducible, including when standing still, and also occurs on repeated visits to the same location.

I tested both Longshot v3.0.0-rc.3 and the Nightly builds, with similar performance problems.

Performance measurements:

GPU utilization: approximately 50–60%
Total CPU utilization: approximately 62–67%
Renderer time: approximately 44–46 ms in the most demanding scene
GPU time: approximately 14–17 ms in the same demanding area
VRAM usage: approximately 6–7 GB
Approximately 3,300–3,400 draw calls per frame

Reducing the internal rendering resolution to 50% did not noticeably improve FPS, suggesting a CPU-side rendering bottleneck rather than a GPU limitation.

I also tested several configuration changes:

HOS_RESERVE_CORE=0: No meaningful improvement.
RX_VK_WB_MAX_KB=1024 with RX_VK_WB_PROBATION=64: No meaningful improvement.
RX_VK_PARALLEL=4: Improved FPS in one demanding scene to approximately 32 FPS and reduced renderer time to around 20 ms. However, overall performance became worse because areas that previously exceeded 40 FPS were now limited to approximately 32–34 FPS.

I reverted these experimental changes.

It appears that CPU-side Vulkan rendering or synchronization may be limiting performance, despite the GPU having considerable unused capacity.

Could the developers investigate whether the CPU-side renderer can be further optimized, especially for virtualized AMD EPYC processors?

My goal is to achieve more consistent performance, ideally approaching 60 FPS without reducing visual quality.

Where in the game

Kokiri Forest, especially when standing still and looking across the village from certain viewpoints, near the beginning of the game. Bit it also happens on every location in the game.

How often

Every time

Graphics card and driver version

NVIDIA RTX A4500 20 GB, driver 621.14

CPU, RAM and operating system

AMD EPYC 7543P (4 vCPU cores / 8 threads, Shadow Power Pro), 28 GB RAM, Windows 11

Changes from the defaults

Output resolution: 1920x1080 at 60 Hz
Game frame rate cap: 60 FPS
Frame generation: Disabled
Frame pacing: Disabled
Windows power plan: Bitsum Highest Performance (ParkControl)
NVIDIA power management: Prefer maximum performance
NVIDIA shader cache size: Unlimited

Experimental configuration settings tested individually and subsequently reverted:

HOS_RESERVE_CORE=0
RX_VK_WB_MAX_KB=1024
RX_VK_WB_PROBATION=64
RX_VK_PARALLEL=4

MSI Afterburner and RivaTuner were used for performance monitoring. The same performance problems existed before monitoring was enabled.

longshot_log.txt

Screenshots or video

Before you send it

The problem is still there on the newest release or nightly.
I searched the open issues for it.
I'm not attaching game files, keys, the game's executable, its .bin caches or saves.

### Longshot version longshot nightly-130-0caf0618 ### Channel Release candidate ### What kind of problem Low fps or stutter ### What happened I'm experiencing significant performance issues in Kokiri Forest, particularly when looking across the village from certain viewpoints. My system is a Shadow Power Pro cloud PC with a virtualized AMD EPYC 7543P CPU (4 physical cores / 8 logical processors), an NVIDIA RTX A4500 20 GB GPU, and 28 GB RAM. At 1920x1080 output resolution, performance usually ranges between 30 and 42 FPS, but drops to approximately 21–24 FPS when looking across the village. This issue is reproducible, including when standing still, and also occurs on repeated visits to the same location. I tested both Longshot v3.0.0-rc.3 and the Nightly builds, with similar performance problems. Performance measurements: - GPU utilization: approximately 50–60% - Total CPU utilization: approximately 62–67% - Renderer time: approximately 44–46 ms in the most demanding scene - GPU time: approximately 14–17 ms in the same demanding area - VRAM usage: approximately 6–7 GB - Approximately 3,300–3,400 draw calls per frame Reducing the internal rendering resolution to 50% did not noticeably improve FPS, suggesting a CPU-side rendering bottleneck rather than a GPU limitation. I also tested several configuration changes: - HOS_RESERVE_CORE=0: No meaningful improvement. - RX_VK_WB_MAX_KB=1024 with RX_VK_WB_PROBATION=64: No meaningful improvement. - RX_VK_PARALLEL=4: Improved FPS in one demanding scene to approximately 32 FPS and reduced renderer time to around 20 ms. However, overall performance became worse because areas that previously exceeded 40 FPS were now limited to approximately 32–34 FPS. I reverted these experimental changes. It appears that CPU-side Vulkan rendering or synchronization may be limiting performance, despite the GPU having considerable unused capacity. Could the developers investigate whether the CPU-side renderer can be further optimized, especially for virtualized AMD EPYC processors? My goal is to achieve more consistent performance, ideally approaching 60 FPS without reducing visual quality. ### Where in the game Kokiri Forest, especially when standing still and looking across the village from certain viewpoints, near the beginning of the game. Bit it also happens on every location in the game. ### How often Every time ### Graphics card and driver version NVIDIA RTX A4500 20 GB, driver 621.14 ### CPU, RAM and operating system AMD EPYC 7543P (4 vCPU cores / 8 threads, Shadow Power Pro), 28 GB RAM, Windows 11 ### Changes from the defaults - Output resolution: 1920x1080 at 60 Hz - Game frame rate cap: 60 FPS - Frame generation: Disabled - Frame pacing: Disabled - Windows power plan: Bitsum Highest Performance (ParkControl) - NVIDIA power management: Prefer maximum performance - NVIDIA shader cache size: Unlimited Experimental configuration settings tested individually and subsequently reverted: - HOS_RESERVE_CORE=0 - RX_VK_WB_MAX_KB=1024 - RX_VK_WB_PROBATION=64 - RX_VK_PARALLEL=4 MSI Afterburner and RivaTuner were used for performance monitoring. The same performance problems existed before monitoring was enabled. ### longshot_log.txt . ### Screenshots or video . ### Before you send it - [x] The problem is still there on the newest release or nightly. - [x] I searched the open issues for it. - [x] I'm not attaching game files, keys, the game's executable, its .bin caches or saves.

Longshot_01_Baseline_ohne_RX_VK_PARALLEL.png

209 KiB

Longshot_02_Test_mit_RX_VK_PARALLEL_4.png

1.3 MiB

report.txt

3.8 KiB

longshot_log.txt

848 KiB

LeFaxen added the

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2026-11-14 10:45:52 +00:00

LeFaxen changed title from ~~Game: Game: [Performance] Severe CPU-side rendering bottleneck in Kokiri Forest (21–42 FPS, low GPU usage)~~ to [Performance] Severe CPU-side rendering bottleneck in Kokiri Forest (21–42 FPS, low GPU usage)

2026-11-14 13:56:00 +00:00