Re: [RFC] Documentation about unaligned memory access

Arnaldo Carvalho de Melo
2007-11-27T00:40:52Z

Em Mon, Nov 26, 2007 at 03:47:06PM +0100, Johannes Berg escreveu:
>
> > Sidenote: in the above example, you may wish to reorder the fields in the
> > above structure so that the overall structure uses less memory. For example,
> > moving field3 to sit inbetween field1 and field2 (where the padding is
> > inserted) would shrink the overall structure by 1 byte:
> >
> > struct foo {
> > u16 field1;
> > u8 field3;
> > u32 field2;
> > };
>
> You can reorder to u32, u16, u8 order and save another byte :)
>
> A reference to pahole could be appropriate here, and probably a small
> note that some large existing structures like netdev have deliberate
> holes to achieve cache alignment.

shameless plug:

https://ols2006.108.redhat.com/2007/Reprints/melo-Reprint.pdf

- Arnaldo