Garbage Collection

Map Of Content

Notes

You pay for memory allocation more than once. The first is obviously when you allocate it. But you also pay every time the garbage collection runs.

Reduce/Reuse/Recycle. — @bboreham

• Stack vs. heap allocations
• What causes heap allocations?
• Understanding Escape Analysis (and the current limitation)
• /debug/pprof/heap , and -base
• API design to limit allocations:
  • allow passing in buffers so caller can reuse rather than forcing an allocation
  • you can even modify a slice in place carefully while you scan over it
  • passing in a struct could allow caller to stack allocate it
• reducing pointers to reduce gc scan times
  • pointer-free slices
  • maps with both pointer-free keys and values
• GOGC
• buffer reuse (sync.Pool vs or custom via go-slab, etc)
• slicing vs. offset: pointer writes while GC is running need writebarrier: https://github.com/golang/go/commit/b85433975aedc2be2971093b6bbb0a7dc264c8fd
  • no writebarrier if writing to stack https://github.com/golang/go/commit/2140975ebde164ea1eaa70fc72775c03567f2bc9
• use error variables instead of errors.New() / fmt.Errorf() at call site (performance or style? interface requires pointer, so it escapes to heap anyway)
• use structured errors to reduce allocation (pass struct value), create string at error printing time
• size classes
• beware pinning larger allocation with smaller substrings or slices