4 ms·

Forgive me. What do you mean by "pack/align things for better perf"? Specifically, in what use cases would this yield better performance? And by what measure

• ygra 12y ago
  Data need to be aligned to multiples of its size on most CPU architectures to access them without performance degradation (or at all, even). Reordering members for smaller object size mostly makes sense so that more of them can fit into cache.
• matthewwarren 12y ago
  It's related to the CPU, there's a nice wiki article[0] that goes into it a bit more. Also in [0] it mentions that SSE instructions will only work with 128-bit aligned data, so sometimes it's a requirement. Alignment can make memory access more efficient, but means that data can take up more space. Packing is the opposite of this, rearranging fields, so that they take up the smallest space possible. So the 2 things are a trade-off. [0] http://en.wikipedia.org/wiki/Data_structure_alignment http://en.wikipedia.org/wiki/Data_structure_alignment