wsl2 perf degrade

[AdamZhong98]

Before you start

• I have read the FAQ and my problem is not answered there.
• I have read the Roadmap and this is not already planned there.
• I have searched existing issues and found no duplicate.
• I am on the latest release, or on a freshly rebuilt main when building from source.

What happened

wsl2 本质是 windows 但 engine 不知道，所以会用 linux 的方式去 pin memory。这个 pin memory 会失败导致大量 fallback 到 pagable memory。

How did you install FreeToken

pip / uv wheel

FreeToken version

v0.2.0-beta.17

OS

Windows 11

OS details

WSL2

GPU and driver

RTX 5090

CPU and system RAM

AMD 9950X3D2 256G

Checkpoint

DeepseekV4 Flash, GLM5.3 Flash

Command

Full log

Anything else

日志.txt

[jason-fxz]

Thanks for the log. Quick summary of what it shows:

WSL2 has the same pinned-memory cap as native Windows. WDDM limits CUDA pinned host memory to roughly 50% of RAM, and WSL2 inherits it. The engine already detects WSL and budgets for this: that is the pin budget 88.08 GiB line. DSV4-Flash's expert banks are 137 GiB, so only 27 layers get pinned and the remaining 16 head/tail layers run on the CPU executor.

The residency fallback chain is pinned -> mlock -> pageable. Layers that don't fit the pin budget are mlock'd instead; if mlock fails they stay pageable. In your case mlock failed because of WSL's default RLIMIT_MEMLOCK (ulimit -Hl is tiny in a WSL session and can't be raised without root). That's a WSL environment issue, not the engine. It should have no effect on the hot path: CPU-layer decode reads the same memory either way, and the only difference is swap protection. Your own log confirms no swapping: decode stays ~15 tok/s across both turns, including after 5 minutes idle.

The slowdown itself comes from the split, not from pageable memory. Because not all banks can be pinned, 16 of 43 MoE layers decode on the CPU, and that's simply slower than the all-GPU offload path. That's inherent to the WDDM cap on Windows/WSL2. The only way around it is native Linux, where nothing caps pinning and all 137 GiB would be pinned.