intel-performance-skills

Detect and fix x86/C/C++ performance patterns from source code or profiling output (perf, VTune, flamegraphs). Invoke when the user asks to optimize, review for performance, or write new SIMD/vectorized code — even without profiling data. Trigger on: serial accumulator loops, narrow SIMD (xmm/ymm that could be ymm/zmm), _mm* intrinsics, HITM/cmpxchg clusters, false sharing, missing restrict or vzeroupper, futex_wake/notify_all thundering herd, hot symbol inside a system library (.so) with a version gap, or any request to write a fast reduction, dot product, or CPU-dispatched function. Patterns: serial accumulator, TTAS spinlock, SIMD upconversion (zipper), false sharing, per-CPU stats, missing vzeroupper, missing restrict, cv-thundering-herd, mutex-to-rwlock, CPU dispatch, library version upgrade, fast CRC32C, known algorithms (Cosine Similarity, Hamming Distance, Jaccard Distance), SIMD sort (x86-simd-sort).

Profile and fix Linux performance problems using `perf`. Workflows: (A) hardware counters -- IPC, cache-miss, branch mispredictions; (B) hotspot profiling -- which functions and source lines consume CPU, with SIMD and accumulator detection; (C) cache-line contention -- false sharing, HITM, `perf c2c`; (D) core-count scaling -- dual-profile comparison, bottleneck categorization; (E) structured hotspot report with annotated source and pattern observations. Resolution strategies: TTAS spinlock, SIMD upconversion, parallel accumulator, structured false-sharing fix, per-CPU stats. Trigger on: perf, profiling, profile, hotspot, hotspots, cache miss, IPC, false sharing, HITM, scaling, core count, thread scaling, bottleneck, slow code, CPU bound, why is this slow, where does time go, does not scale. When in doubt, invoke this skill -- better to use it unnecessarily than to miss a performance opportunity.

Install, run, parse, and optimize benchmarks from the Phoronix Test Suite (PTS). Use this skill whenever the user mentions "phoronix", "pts/", or "phoronix-test-suite", or asks to run, measure, improve, or optimize a PTS test — e.g., "run pts/mt-dgemm", "optimize pts/compress-zstd", "what score does pts/x265 get". Trigger immediately on any `pts/<testname>` reference, even if the user doesn't explicitly say "phoronix". Also trigger when the user asks to find or edit the source code of a PTS test.