golang-performance

Profile first with pprof to find the actual bottleneck rather than guessing. Write an atomic benchmark, measure a baseline with -benchmem and -count=6, apply one optimization at a time, then compare results with benchstat for statistical significance.

Reuse slice backing arrays with append(s[:0], ...), preallocate maps and slices with size hints, use sync.Pool for frequently allocated short-lived objects, and avoid interface boxing by using typed parameters or generics.

Use fgprof, which captures both on-CPU and off-CPU time such as I/O wait and blocked goroutines. Standard pprof CPU profiles only show on-CPU time, so they appear empty when the bottleneck is external like a slow database or network call.

Yes. Go inserts padding between fields to satisfy alignment requirements, so ordering fields from largest to smallest reduces struct size. Use the fieldalignment tool to detect structs with wasted padding automatically.

Avoid sync.Pool for objects larger than about 32KB, infrequently allocated objects, and cases where callers retain references to pooled buffers. Always reset state before Put and return copies rather than the pooled buffer itself.

Go maps never release bucket memory when entries are deleted, so a map that once held millions of keys retains its peak allocation. Replace the map with a fresh make() call so the old bucket array becomes eligible for garbage collection.