Re: ZONE_PADDING wastes 4 bytes of the new cacheline

[Nick Piggin]

Andrew Morton wrote:
> Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
>
> > > #if defined(CONFIG_SMP)
> >
> > >  struct zone_padding {
> > > -	int x;
> > >  } ____cacheline_maxaligned_in_smp;
> > >  #define ZONE_PADDING(name)	struct zone_padding name;
> > >  #else
> >
> > Perhaps to keep old compilers working? Not sure.
>
>
> gcc-2.95 is OK with it.
>
> Stock 2.6.9:
>
> 	sizeof(struct zone) = 1920
>
> With Andrea's patch:
>
> 	sizeof(struct zone) = 1536
>
> With ZONE_PADDING removed:
>
> 	sizeof(struct zone) = 1408
> 	

Wow. You'd probably still want pad1 because that seperates the
allocator and the scanner. It looks like temp/prev_priority
should be _above_ pad2, and possibly free_area should be above
pad1.

Don't know about all the stuff below pad3.
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