CPU cache optimization skill for C/C++ and Rust. Use when diagnosing cache misses, improving data layout for cache efficiency, using perf stat cache counters, understanding false sharing, prefetching, or structuring AoS vs SoA data layouts. Activates on queries about cache misses, cache lines, false

CPU Cache Optimization Purpose Guide agents through cache aware programming: diagnosing cache misses with perf, data layout transformations (AoS→SoA), false sharing detection and fixes, prefetching, and cache friendly algorithm design. Triggers "My program has high cache miss rates — how do I fix it?" "What is false sharing and how do I detect it?" "Should I use AoS or SoA data layout?" "How do I measure cache performance with perf?" "How do I use builtin prefetch?" "My multithreaded program is slower than single threaded due to cache" Workflow 1. Measure cache performance 2. Cache line basics Cache line size: 64 bytes on x86 64, ARM (most platforms) L1 cache: 32–64 KB, ~4 cycles latency L2 cache: 256 KB–1 MB, ~12 cycles latency L3 cache: 6–64 MB, ~40 cycles latency Main memory: ~200–300 cycles latency 3. AoS vs SoA data layout 4. Common cache unfriendly patterns 5. False sharing False sharing occurs when two threads write to different variables that share a cache line, causing constant cache line invalidations. 6. Prefetching Manual prefetch hints to hide memory latency: Prefetching rules: Prefetch too early = cache evicted before use Prefetch too late = no benefit Prefetch distance = memory latency / time per iteration (typically 8–32 elements) 7. Cache friendly algorithm design For perf cache event reference and false sharing detection patterns, see [references/cache counters.md](references/cache counters.md). Related skills Use skills/profilers/linux perf for perf stat and perf record cache measurements Use skills/profilers/valgrind — cachegrind simulates cache behaviour Use skills/low level programming/simd intrinsics — SoA layout pairs with SIMD vectorization Use skills/low level programming/memory model for false sharing in concurrent contexts

cpu-cache-opt