AIME 2025 + GSM8K at TP=1/2/4. Quality on par across engines/TP. Opposite
perf scaling: xserv TPOT improves with TP (21->17->15ms) while llama.cpp
row-split regresses over PCIe (10->19->20ms), crossing over so xserv is faster
at TP=4. Includes the clean same-path bench-tp scaling (58/76/86 tok/s).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Megatron-style TP for Qwen3 on the 8x5090 (no-NVLink, PCIe) box: column/row
split per layer, 2 AllReduces/layer, multi-thread one-rank-per-GPU model,
NCCL, sharded weights, and the incremental implementation + verification plan.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Re-ran the full comparison at --max-seq-len 8192 now that xserv handles it:
- OOM finding resolved — pool sized to available VRAM + vLLM-style host swap;
8192 runs with 0 swap events (swap is the overload safety net).
- Quality at parity with equal context: AIME 20.0% vs 20.0%, GSM8K 98% vs 96%.
- Speed unchanged relative to llama.cpp (~0.42-0.60x); TPOT is bandwidth-bound.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Record what the new baseline adds (llama.cpp pinned b9371, same BF16 weights,
AIME 2025 + GSM8K) and the measured results: performance (xserv ~0.45-0.61x
llama.cpp throughput) and quality parity (GSM8K 94% vs 96%, AIME 23.3% vs 20%
after the context fix), plus the findings the bench surfaced.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Refinements from end-to-end bring-up on the GPU host:
- Run each system start→suites→stop in sequence. Two BF16 8B models don't
co-reside on one 32GB GPU, and a resident idle engine would distort the
other's latency/throughput.
- Match generation mode: xserv hardcodes Qwen3 thinking off, so send
chat_template_kwargs={enable_thinking:false} to llama.cpp via a per-endpoint
extra_body. --enable-thinking opts back into thinking mode.
- Add tools/__init__.py so `python3 -m tools.bench.runner` resolves our package
instead of a site-packages `tools` (nvfuser ships one that shadowed it).
- Document offline-GPU-host workflow, thinking-match, and the xserv 8192 OOM
finding that the bench surfaced.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Vendor llama.cpp as a submodule pinned to b9371 and add a one-click
benchmark driver that compares xserv against it on identical workloads:
- setup-llama-cpp.sh: network-optional CUDA build (SM120); convert-to-gguf.sh
converts the same safetensors to BF16 GGUF for an apples-to-apples baseline.
- tools/bench/: black-box OpenAI-API driver measuring TTFT/TPOT/throughput
(single-stream + concurrent) and response quality on AIME 2025 + GSM8K.
- fetch_datasets.py pulls datasets to local JSON (GPU host has no network);
task loaders prefer the local JSON.
- sync-and-build.sh: `bench` subcommand transfers source + datasets to the
GPU host via tar-over-ssh (no rsync there), builds, and runs the suite.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
New crate: xserv-server
- Engine thread: loads Qwen3-8B, processes requests sequentially
- axum HTTP server: /health, /v1/models, /v1/chat/completions
- tokio::sync::mpsc channel between API and engine threads
- Non-streaming JSON response (streaming SSE to be added later)
API is OpenAI-compatible:
POST /v1/chat/completions {"messages": [...], "max_tokens": N}
→ {"choices": [{"message": {"content": "..."}}]}
Verified: "Hi" → ", I'm" (3 tokens), model runs correctly via HTTP.
Key learnings:
- std::sync::mpsc::SyncSender is Send but NOT Sync → wrap in Mutex for Arc<AppState>
- MutexGuard must not live across await points (scope carefully)
- axum 0.8 Extension<Arc<T>> requires T: Send + Sync
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- GpuKVCache: pre-allocated GPU buffers, D2D copy append at offset
- Per-head strided layout [num_kv_heads, max_seq_len, head_dim]
- Fixed critical bug: seq_len must advance AFTER all layers write
(not inside the loop per-layer)
- GpuBuffer::copy_from_device_at for offset-based D2D copy
- Tensor::from_storage constructor for wrapping raw GPU buffers
- Exported Storage and Dims from xserv-tensor
Correctness: GPU KV cache vs CPU KV cache = 50/50 bit-identical
Performance: ~neutral (KV cache was never the main bottleneck —
reshape/merge/transpose CPU round-trips dominate for Qwen3-8B)
TTFT: 122ms, TBT: 142ms, 7.0 tok/s (marginal change from 7.3)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Qwen3 model (qwen3.rs):
- RMSNorm + QK normalization (per-head q_norm/k_norm)
- GQA: 32 Q heads, 8 KV heads, repeat_kv for attention
- SwiGLU FFN: gate_proj → SiLU → * up_proj → down_proj
- RoPE with transpose for [1,H,S,D] ↔ [S,H,D] layout
- BF16 forward pass, [out,in] weight layout via linear_t
- No attention bias (attention_bias=false)
Tokenizer fixes:
- Fixed unicode_to_byte: shifted bytes now use correct inverse lookup table
- MergeEntry supports both string and array formats
- Both GPT-2 and Qwen3 tokenizers work correctly (English + Chinese)
KVCache refactored:
- Dtype-agnostic: stores raw bytes per-head, works for F32 and BF16
- append_kv_tensor/get_kv_tensors use Tensor directly
CLI updated:
- Auto-detects model type from config.json (gpt2 vs qwen3)
- Supports both GPT-2 (F32) and Qwen3 (BF16)
Verified: Qwen3-8B generates coherent English and Chinese on single RTX 5090.
61/61 tests pass, GPT-2 performance no regression.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Phase 6 — Model Loading (xserv-model):
- safetensors parser with single/sharded file support
- ModelConfig with dual naming (GPT-2 n_embd/n_head + modern HF naming)
- Weight loading flow: safetensors → mmap → CPU Tensor → GPU
Phase 7 — BPE Tokenizer (xserv-tokenizer):
- Full BPE encode/decode from tokenizer.json
- GPT-2 byte-to-unicode mapping (printable ASCII identity + shifted bytes)
- Pre-tokenization regex, special token handling
- Chat template support structure
Phase 8 — GPT-2 Complete Inference:
- GPT-2 model definition: wte, wpe, 12 transformer blocks, ln_f
- Forward pass: embedding → (LayerNorm → MHA → residual → LayerNorm → MLP → residual) × 12 → LN → logits
- QKV split with correct [batch, heads, seq, dim] layout (fixed reshape bug)
- Greedy sampling from last-position logits
- Interactive CLI: xserv-cli <model-dir> [--max-tokens N]
Verified: GPT-2 124M generates coherent English text on RTX 5090.
"The future of AI is uncertain. The future of AI is uncertain..."
"Once upon a time, the world was a place of great beauty..."
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- Cargo workspace with xserv-cuda crate
- CUDA FFI bindings (cudart: memory, stream, device, error)
- GpuBuffer RAII wrapper with H2D/D2H/D2D copy
- CudaStream wrapper with RAII Drop
- CachingAllocator with size-bucketed free lists
- PinnedBuffer for page-locked host memory
- Device info query via cudaDeviceGetAttribute
- Vector-add CUDA kernel smoke test
- Integration test suite (11 tests)
- build.rs: cc crate compiles .cu for SM 12.0
- sync-and-build.sh for remote build on dash5
- Roadmap doc (docs/00-roadmap.md) and Phase 0+1 design doc
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
