vLLM Request Lifecycle: From OpenAI API to One Forward Pass
· ☕ 8 min read · âœī¸ k4i
A source-reading walkthrough of the vLLM V1 request path: OpenAI-compatible HTTP entrypoint, serving render, AsyncLLM, EngineCore client, Tensor IPC, scheduler, and one GPUModelRunner forward pass.
vLLM Request Lifecycle: From OpenAI API to One Forward Pass
LLM Attention Kernels and GPU Primitives
· ☕ 1 min read · âœī¸ k4i
A series index for LLM attention kernels and GPU primitives: fused softmax, online softmax, FlashAttention, PagedAttention kernels, Triton/CUDA, and memory-access optimization.
LLM Attention Kernels and GPU Primitives
LLM Quantization and Low-Precision Serving
· ☕ 1 min read · âœī¸ k4i
A series index for LLM quantization and low-precision serving: INT8/INT4, GPTQ, AWQ, SmoothQuant, NF4, AQLM, KV cache quantization, FP8 serving, and quality/speed/memory tradeoffs.
LLM Quantization and Low-Precision Serving
Disaggregated Prefill: Splitting Compute Across Machines
· ☕ 9 min read · âœī¸ k4i
Routing prefill and decode to separate GPU pools eliminates interference entirely, enabling independent scaling and optimal latency — at the cost of KV cache migration across machines.
Disaggregated Prefill: Splitting Compute Across Machines
Prefix Caching: Reusing KV Cache Across Requests
· ☕ 8 min read · âœī¸ k4i
When thousands of requests share the same system prompt, recomputing its KV cache each time is pure waste. Prefix caching stores and reuses those vectors, cutting TTFT by up to 97% in common deployments.
Prefix Caching: Reusing KV Cache Across Requests
Paged Attention: Virtual Memory for the GPU
· ☕ 10 min read · âœī¸ k4i
How vLLM borrows the OS paging idea to eliminate KV cache memory fragmentation, pushing GPU utilization from ~30% to ~96%.
Paged Attention: Virtual Memory for the GPU
Why KV Cache Works in LLM Inference
· ☕ 9 min read · âœī¸ k4i
why the key-value cache avoids redundant computation in autoregressive decoding, and the memory/compute tradeoffs it introduces.
Why KV Cache Works in LLM Inference
Fused Softmax in Triton
· ☕ 7 min read · âœī¸ k4i
how to write a fused softmax kernel in triton that eliminates redundant memory accesses and outperforms pytorch's native implementation.
Fused Softmax in Triton