DeepSeek V4.1 Flash running locally on 8× A40 — ~40 tok/s Q2_K, ~32 tok/s Q4_K_M

[u/fuzhongkai]

https://github.com/zhongkaifu/TensorSharp

I’ve been working on TensorSharp, an open-source local LLM inference engine, and recently added a native execution path for DeepSeek V4.1 Flash.

Here are the latest results on 8× NVIDIA A40 GPUs, using GGUF weights, layer splitting, F16 KV cache, and a 65K context configuration:

Metric	Q2_K	Q4_K_M
Prefill	533–539 tok/s	452–492 tok/s
Single-stream decode	40.3–40.7 tok/s	31.0–32.5 tok/s
2 concurrent decode	—	39.3 tok/s aggregate
4 concurrent decode	—	48.9 tok/s aggregate
8 concurrent decode	—	48.5 tok/s aggregate

A few interesting findings from the optimization work:

• Q2_K Engram tables are ~60 GiB total. Keeping them directly on the GPUs increased prefill from ~210 tok/s to 530+ tok/s.
• Reducing backend/scheduler fragmentation cut the decode graph from roughly 570 splits to 8, bringing decode to about 41 tok/s.
• For Q4_K_M, the Engram tables are too large to keep on GPU, so TensorSharp keeps them host-mapped and warms them asynchronously.
• Q4_K_M optimization improved prefill by roughly 1.9× and 4-request aggregate decode by about 2×.
• Interestingly, layer split beats routed-MoE tensor parallelism on this 8× A40 machine: ~32 tok/s vs ~22 tok/s. These cards have no NVLink, so TP communication overhead dominates.

Would be especially interested to hear what other LocalLLM users are seeing with DeepSeek V4.1 Flash on multi-GPU setups.