# Activation Memory Anatomisi: Niye O(L·s·h) ve FlashAttention'ın Gerçek Tasarrufu

> Source: https://sukruyusufkaya.com/learn/fine-tuning-cookbook/ftc-activation-memory-anatomy-flashattention
> Updated: 2026-08-22T19:18:02.192Z
> Category: Fine-Tuning Cookbook (Model-by-Model)
> Module: Part I — Hardware & Memory Engineering
**TLDR:** Activation memory: forward pass'in en yanıltıcı bellek tüketicisi. Layer-by-layer breakdown (attn intermediates, FFN, norm, residual), FlashAttention'ın saved memory matematiği (O(s²)'den O(s)'e), grad-checkpoint'in 'sqrt(L) tasarruf' efsanesi, packing + variable-length attention.