Aggressively optimize Ollama CPU inference speed

- Warm up both models on startup with keep_alive=24h (no cold starts)
- Use 16 threads for inference (server has 20 cores)
- Reduce context window to 1024 tokens, max output to 256
- Persistent httpx client for embedding calls (skip TCP handshake)
- Trim RAG chunks to 300 chars, history to 4 messages
- Shorter system prompt and context wrapper

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/embeddings.py

@@ -12,11 +12,23 @@ from app.models import Experience, Substance, DocumentChunk
 
 logger = logging.getLogger(__name__)
 
+# Persistent HTTP client for Ollama calls (avoids TCP handshake per request)
+_ollama_client: httpx.AsyncClient | None = None
+
+
+def _get_ollama_client() -> httpx.AsyncClient:
+    global _ollama_client
+    if _ollama_client is None or _ollama_client.is_closed:
+        _ollama_client = httpx.AsyncClient(
+            base_url=settings.ollama_base_url,
+            timeout=httpx.Timeout(connect=10, read=120, write=10, pool=10),
+        )
+    return _ollama_client
+
 
 def chunk_text(text: str, chunk_size: int = 500, overlap: int = 50) -> list[str]:
     """Split text into overlapping chunks by approximate token count (words / 0.75)."""
     words = text.split()
-    # Approximate: 1 token ~ 0.75 words
     words_per_chunk = int(chunk_size * 0.75)
     words_overlap = int(overlap * 0.75)
 
@@ -36,25 +48,18 @@ def chunk_text(text: str, chunk_size: int = 500, overlap: int = 50) -> list[str]
 
 async def get_embedding(text: str, client: httpx.AsyncClient | None = None) -> list[float]:
     """Get embedding vector for text using Ollama."""
-    should_close = False
-    if client is None:
-        client = httpx.AsyncClient(timeout=60)
-        should_close = True
+    c = client or _get_ollama_client()
 
-    try:
-        resp = await client.post(
-            f"{settings.ollama_base_url}/api/embeddings",
-            json={
-                "model": settings.ollama_embed_model,
-                "prompt": text,
-            },
-        )
-        resp.raise_for_status()
-        data = resp.json()
-        return data["embedding"]
-    finally:
-        if should_close:
-            await client.aclose()
+    resp = await c.post(
+        "/api/embeddings",
+        json={
+            "model": settings.ollama_embed_model,
+            "prompt": text,
+        },
+    )
+    resp.raise_for_status()
+    data = resp.json()
+    return data["embedding"]
 
 
 async def get_embeddings_batch(texts: list[str], client: httpx.AsyncClient) -> list[list[float]]:

app/llm.py

@@ -8,6 +8,8 @@ from app.config import settings
 
 logger = logging.getLogger(__name__)
 
+_stream_timeout = httpx.Timeout(connect=10, read=300, write=10, pool=10)
+
 
 async def stream_ollama(messages: list[dict], system: str = "") -> AsyncGenerator[str, None]:
     """Stream a chat completion from Ollama."""
@@ -20,14 +22,16 @@ async def stream_ollama(messages: list[dict], system: str = "") -> AsyncGenerato
         "model": settings.ollama_chat_model,
         "messages": all_messages,
         "stream": True,
+        "keep_alive": "24h",
         "options": {
-            "num_ctx": 2048,
-            "num_predict": 512,
+            "num_ctx": 1024,
+            "num_predict": 256,
+            "num_thread": 16,
+            "temperature": 0.7,
         },
     }
 
-    timeout = httpx.Timeout(connect=30, read=600, write=30, pool=30)
-    async with httpx.AsyncClient(timeout=timeout) as client:
+    async with httpx.AsyncClient(timeout=_stream_timeout) as client:
         async with client.stream(
             "POST",
             f"{settings.ollama_base_url}/api/chat",

app/main.py

@@ -5,6 +5,7 @@ import uuid
 from contextlib import asynccontextmanager
 from pathlib import Path
 
+import httpx
 from fastapi import FastAPI, Request
 from fastapi.responses import HTMLResponse, StreamingResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
@@ -20,11 +21,38 @@ logger = logging.getLogger(__name__)
 sessions: dict[str, list[dict]] = {}
 
 
+async def warmup_models():
+    """Pre-load chat and embedding models into Ollama memory."""
+    try:
+        async with httpx.AsyncClient(timeout=120) as client:
+            # Warm up embedding model
+            logger.info(f"Warming up embedding model: {settings.ollama_embed_model}")
+            await client.post(
+                f"{settings.ollama_base_url}/api/embeddings",
+                json={"model": settings.ollama_embed_model, "prompt": "warmup"},
+            )
+            # Warm up chat model with keep_alive to hold in memory
+            logger.info(f"Warming up chat model: {settings.ollama_chat_model}")
+            await client.post(
+                f"{settings.ollama_base_url}/api/generate",
+                json={
+                    "model": settings.ollama_chat_model,
+                    "prompt": "hi",
+                    "options": {"num_predict": 1, "num_thread": 16},
+                    "keep_alive": "24h",
+                },
+            )
+            logger.info("Models warmed up and loaded into memory.")
+    except Exception as e:
+        logger.warning(f"Model warmup failed (will load on first request): {e}")
+
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     logger.info("Initializing database...")
     await init_db()
     logger.info("Database ready.")
+    await warmup_models()
     yield
 
 

app/rag.py

@@ -76,8 +76,7 @@ def build_context_prompt(chunks: list[dict]) -> str:
             header += f" | Substance: {metadata['substance']}"
         header += " ---"
 
-        # Limit each chunk to avoid overwhelming the LLM
-        content = chunk["content"][:500]
+        content = chunk["content"][:300]
         context_parts.append(f"{header}\n{content}")
 
     return "\n\n".join(context_parts)
@@ -93,13 +92,12 @@ async def chat_stream(
 
     # Build the context-augmented system prompt
     context_text = build_context_prompt(chunks)
-    full_system = f"{SYSTEM_PROMPT}\n\n--- RELEVANT EROWID DATA ---\n{context_text}\n--- END EROWID DATA ---"
+    full_system = f"{SYSTEM_PROMPT}\n\nContext:\n{context_text}"
 
-    # Build message history
+    # Build message history (keep minimal for speed)
     messages = []
     if conversation_history:
-        # Keep last 6 messages for context
-        messages = conversation_history[-6:]
+        messages = conversation_history[-4:]
 
     messages.append({"role": "user", "content": user_message})