[zeusk]

The real issue with packed structs and bitfields happens when concurrency gets involved. Majority of modern CPU caches are private and only allow one core to hold the cache line - so it creates more false dependencies when cores are trying to alter information that was compacted into a cache line on another core.

[charleslmunger]

Avoiding false sharing is a separate problem best solved by explicitly aligning the struct or relevant members to std::hardware_destructive_interference_size.