Type alignment (understanding memory layout)

[scottmcm]

Re-using an old post about why chips care about alignment:

Std::ptr::read behavior

It's because on some architectures you can't do unaligned reads, and sometimes there are more efficient instructions available if things are aligned. For example, movaps vs movups in x64. For a chip, it's much easier to not have to worry about potentially updating two different cache lines coherently needing two different TLB pages handling two different memory protection levels needing two different RAM sticks needing two different chips on those RAM sticks etc The big desktop chips have …