message: global_heap: improve freeFor performance
diff: @@ -83,10 +83,11 @@ void GlobalHeap::freeFor(MiniHeap *mh, void *ptr, size_t startEpoch) {
  if (_lastMeshEffective.load(std::memory_order::memory_order_acquire) == 0) {
  _lastMeshEffective.store(1, std::memory_order::memory_order_release);
  }
  + // read inUseCount before calling free to avoid stalling after the
  + // LOCK CMPXCHG in mh->free
  + auto remaining = mh->inUseCount() - 1;
  mh->free(arenaBegin(), ptr);
  - auto remaining = mh->inUseCount();
  -
  bool shouldMesh = false;
  // the epoch will be odd if a mesh was in progress when we looked up
  