Re: Reduce struct page by 8 bytes on 64bit

[Andi Kleen]

On Wed, Apr 16, 2003 at 11:40:35PM +0200, David S. Miller wrote:
>    From: Andrew Morton <[e-mail]>
>    Date: Wed, 16 Apr 2003 14:43:11 -0700
>    
>    Well are we sure that the `flags' and `count' fields will always fall into
>    the same 256-byte range?  Wouldn't it subtly break if sizeof(struct page)
>    became not a multiple of eight?  Will the compiler pad it out anyway?
> 
> As long as there is a long or pointer member, the structure
> will be required to be 8 byte or better aligned.

Yes that should be a safe assumption. mem_map will be always page aligned
and it should be a multiple of a power of 8. That makes it impossible for it
to cross a cache line.

-Andi