CPU LLM #2: The Memory Trick That Makes Multi-Core CPUs Fly for AI

Ever wondered why adding more CPU cores doesn't always make your AI models faster? The problem often lies in a hidden hardware bottleneck called "false sharing." In this deep dive, we uncover the memory layout trick that solves this issue and unlocks true, linear performance scaling for AI on multi-core CPUs.

Building on the brilliant foundation of Andrej Karpathy's llama2.c, we analyze why simple sequential memory allocation, while great for single-threaded performance, hits a wall in parallel processing. I'll break down the complex topic of cache coherency and false sharing step-by-step using detailed infographics.

Then, we'll walk through the complete C code for a "bump" allocator that creates a perfectly cache-aligned, single-block memory layout. You'll see how this low-level optimization strategy minimizes cache misses, eliminates TLB churn with huge pages, and allows our code to achieve near-perfect performance scaling.

In this video, you will learn:
The difference between sequential and cache-aligned memory layouts.
What False Sharing is and why it kills parallel performance.
How to implement a "bump" allocator in C for perfect memory alignment.
How to structure memory for high-performance, multi-core AI workloads.

📦 Source Code (Release v0.1.0)
→ https://github.com/antshiv/C-Transfor...

🔎 Browse the code at this version:
→ https://github.com/antshiv/C-Transfor...

💻 Clone and checkout:
git clone https://github.com/antshiv/C-Transfor...
cd C-Transformer
git checkout v0.1.0

🧠 Read the release notes for architecture details.

Karapathy's GPT-2 C code: https://github.com/karpathy/llm.c/blo...

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The handheld controller code:
]
► https://github.com/antshiv/BLEHandhel...

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DISCLAIMERS:
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.

This video was not paid for by outside persons or manufacturers.
No gear was supplied to me for this video.

The content of this video and my opinions were not reviewed or paid for by any outside persons.