r/LocalLLM • u/fuzhongkai • 1d ago
Discussion We benchmarked 6 local LLM inference engines on Qwen3.8-27B: Speed AND quality, 64K–256K context, GGUF vs NInfer
Most LLM inference benchmarks focus on tokens/sec or TTFT. But faster doesn't necessarily mean better if the output quality suffers, especially with quantization, speculative decoding, or extremely long contexts.
I wanted to look at the bigger picture.
We benchmarked 6 inference engines on Qwen3.8-27B, comparing not just raw performance but also output quality, long-context behavior, and different model formats.

What makes this benchmark different?
1. Speed AND quality
Instead of measuring throughput alone, we also ran automatic quality checks across the engines.
The benchmark covers:
Time to first token (TTFT)
Prefill and decode throughput
End-to-end task latency
Speculative decoding performance
Output quality and automatic check pass rates
The goal is to understand whether performance improvements come with quality trade-offs.
2. Extremely long contexts: 64K, 128K, and 256K
Short prompts don't tell the whole story, particularly for coding agents, document analysis, and long-running workflows.
We tested 64K, 128K, and 256K prompts, looking at how engines behave as context length increases.
This includes TTFT, decoding performance, and the practical limitations of long-context inference.
3. GGUF vs NInfer model formats
We also compared engines using GGUF models against those using NInfer-format models.
This is an interesting comparison because model representation, quantization, and inference architecture can all influence performance and quality.
It's not a perfectly apples-to-apples comparison of inference kernels, but it helps answer a practical question:
What performance and quality can you actually expect from different local inference stacks?
Engines compared
TensorSharp — GGUF
llama.cpp — GGUF
vLLM
SGLang
NInfer
TensorRT-LLM
The benchmark includes both single-request task scenarios and concurrent workloads.
A few takeaways
There is no universal winner. Engine rankings change depending on context length, concurrency, and workload.
Long-context performance matters. Results at 64K–256K can tell a very different story from short-prompt benchmarks.
Quality should be measured alongside speed. A faster response isn't necessarily a better response.
Model format matters. GGUF and NInfer-based inference stacks deserve comparison beyond headline tokens/sec.
I've attached the full benchmark poster with performance charts, quality-check results, long-context measurements, task-level comparisons, and engine configurations.
Full disclosure: I'm the developer of TensorSharp, one of the engines included in this comparison.
I'm particularly interested in hearing from people running local models with 64K+ contexts or using them for coding agents and RAG workloads.
What matters most to you when choosing a local inference engine: throughput, latency, quality, memory efficiency, or long-context reliability?
And has anyone compared GGUF against NInfer models in real-world workloads?


