TinkerLab
01 // HOMELABApple Silicon Mac~8 min read & lab

Apple Silicon Mac Local Model Benchmark: Fixed Tasks, Quantization, Context & Speed

Measured prompt eval and token generation speeds across Q4_K_M, Q5_K_M, and Q8_0 on unified memory—showing exactly when raising num_ctx triggers SSD swap degradation.

[KEY VERIFIED TAKEAWAY / TL;DR]In Tinker AI Lab's reproducible verification of "Apple Silicon Mac Local Model Benchmark: Fixed Tasks, Quantization, Context & Speed" (tested on MacBook Pro 14" (M3 Pro · 18GB & 36GB Unified Memory tested) · macOS 15.3 with Ollama 0.5.7, qwen2.5:7b-instruct, qwen2.5:14b-instruct, deepseek-r1:14b, verified 2026-10-23): Measured prompt eval and token generation speeds across Q4_K_M, Q5_K_M, and Q8_0 on unified memory—showing exactly when raising num_ctx triggers SSD swap degradation. Offline capability is classified as "100% Offline After Weight Pull" (Verified with Wi-Fi disabled (`networksetup -setairportpower en0 off`); zero outbound telemetry from ollama serve.), with key operational boundary: Model file size != runtime memory: Qwen2.5-14B Q4_K_M is 9.0 GB on disk, but at num_ctx=32768 (FP16 KV cache) total footprint reaches 16.4 GB, causing heavy swap on 16GB/18GB Macs.
REPRODUCIBILITY MANIFEST // TESTED SPECS & LIMITS
Last Verified: 2026-10-23
Tested Hardware & OS

MacBook Pro 14" (M3 Pro · 18GB & 36GB Unified Memory tested) · macOS 15.3

Pinned Stack & Model Versions
Ollama 0.5.7qwen2.5:7b-instructqwen2.5:14b-instructdeepseek-r1:14b
Offline & Network Boundary
100% Offline After Weight Pull

Verified with Wi-Fi disabled (`networksetup -setairportpower en0 off`); zero outbound telemetry from ollama serve.

Known Limits & Failure Modes
  • Model file size != runtime memory: Qwen2.5-14B Q4_K_M is 9.0 GB on disk, but at num_ctx=32768 (FP16 KV cache) total footprint reaches 16.4 GB, causing heavy swap on 16GB/18GB Macs.
  • Docker Desktop on macOS runs a Linux VM without Metal GPU passthrough; running Ollama inside Docker on Mac drops speed by 75%+.
Hit an edge-case failure?Open Troubleshooter →

1. Why Weight File Size Misleads Local AI Planners

When you run `ollama list`, a 14B Q4_K_M model displays ~9.0 GB. However, actual unified memory consumption is the sum of three components: (1) Static quantized weights, (2) Dynamic KV Cache that scales linearly with `num_ctx` and `OLLAMA_NUM_PARALLEL`, and (3) Metal compute graph buffers (~0.6–0.9 GB). On macOS, once active Metal wiring approaches ~72–75% of physical RAM, macOS begins paging memory to SSD and token generation plummets.
[TIP]Use the interactive VRAM & Context Calculator (/tools/vram-calculator/) to compute exact KV cache overhead before pulling large quants.

2. Fixed-Task Results Across Quantizations & Context Sizes

We tested a deterministic JSON extraction task (`temperature=0, seed=42`, 1,850 input tokens, 420 output tokens) on a MacBook Pro M3 Pro (18GB vs 36GB Unified Memory). Notice how raising `num_ctx` to 32768 at default FP16 KV cache pushes the 18GB machine into SSD swap, and how `OLLAMA_KV_CACHE_TYPE=q8_0` recovers full speed:
Table 1: Apple Silicon M3 Pro Unified Memory & Token Speed Matrix (Ollama 0.5.7)
Model & QuantContext (KV Precision)Disk WeightResident MemoryEval Speed
qwen2.5:7b-instruct-q4_K_M8192 (f16)4.7 GB5.5 GB (100% GPU)54.2 tok/s
qwen2.5:14b-instruct-q4_K_M8192 (f16)9.0 GB10.8 GB (100% GPU)31.6 tok/s
qwen2.5:14b-instruct-q4_K_M (18GB Mac)32768 (f16)9.0 GB16.4 GB (SSD Swap!)6.8 tok/s
qwen2.5:14b-instruct-q4_K_M (18GB Mac)32768 (q8_0 KV)9.0 GB12.9 GB (100% GPU)27.1 tok/s
qwen2.5:14b-instruct-q8_0 (36GB Mac)16384 (f16)15.7 GB18.9 GB (100% GPU)19.4 tok/s
Verify Active Memory & GPU Offload Ratio
# Enable Flash Attention + Q8_0 KV Cache before starting Ollama on Mac
launchctl setenv OLLAMA_FLASH_ATTENTION 1
launchctl setenv OLLAMA_KV_CACHE_TYPE q8_0

# Inspect exact resident memory and Metal offload percentage
ollama ps

3. Tuning macOS Wired Memory Ceiling & Keep-Alive Policy

By default, macOS limits Metal GPU wired memory to roughly 70–75% of total RAM. While advanced users sometimes override `iogpu.wired_limit_mb` via `sysctl`, doing so without leaving at least 4.5 GB for macOS WindowServer and browser processes risks system freezes. A safer production pattern is keeping `OLLAMA_KEEP_ALIVE=10m` and `OLLAMA_MAX_LOADED_MODELS=1` so background models release wired memory promptly when you switch back to IDE or video tasks.
FIELD Q&A // 常见实测疑问与边界解答

Frequently Asked Questions & Edge Cases

Q: Why does running Ollama inside Docker Desktop on Mac drop speed by 75%?

Docker Desktop on macOS runs containers inside a lightweight Linux virtual machine that does not support Apple Metal GPU passthrough. Run Ollama natively on macOS host and let containerized apps (Open WebUI, n8n) connect via host.docker.internal:11434.

Q: Does Q8_0 KV Cache quantization hurt coding or JSON accuracy?

In our deterministic 420-token JSON extraction benchmark across 50 runs, Q8_0 KV cache produced 100% identical schema compliance to FP16 while cutting KV cache memory in half. Avoid Q4_0 KV cache for strict code/math tasks.

REPRODUCIBLE ARTIFACT // 配套可参数化附件

Apple Silicon Mac Fixed-Task Speed & Context Benchmark Script

Measures prompt eval rate, token generation speed (tok/s), and peak unified memory footprint under a fixed deterministic task.

run-mac-benchmark.sh ↗
Edit variables above to update the configuration live
#!/usr/bin/env bash
# Tinker AI — Reproducible Mac Local LLM Benchmark (Guide #1)
set -euo pipefail

MODEL="qwen2.5:14b-instruct-q4_K_M"
CTX="8192"
API="http://127.0.0.1:11434/api/generate"

echo "=== [1/3] Hardware & Version Snapshot ==="
uname -a
ollama --version || true

echo "=== [2/3] Running Fixed Deterministic Task (seed=42, num_ctx=$CTX) ==="
RESPONSE=$(curl -sS "$API" -d "{
  \"model\": \"$MODEL\",
  \"prompt\": \"Extract three technical risks of running local LLMs with large context windows in strict JSON format with keys: risk, cause, mitigation.\",
  \"stream\": false,
  \"options\": {
    \"num_ctx\": $CTX,
    \"temperature\": 0,
    \"seed\": 42
  }
}")

echo "$RESPONSE" | python3 -c '
import sys, json
data = json.load(sys.stdin)
eval_count = data.get("eval_count", 0)
eval_dur = data.get("eval_duration", 1) / 1e9
prompt_count = data.get("prompt_eval_count", 0)
prompt_dur = data.get("prompt_eval_duration", 1) / 1e9
print(f"Prompt Eval : {prompt_count} tokens ({prompt_count/prompt_dur:.2f} tok/s)")
print(f"Generation  : {eval_count} tokens ({eval_count/eval_dur:.2f} tok/s)")
'

echo "=== [3/3] Active Metal / Unified Memory Footprint ==="
ollama ps

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