Re: ZONE_PADDING wastes 4 bytes of the new cacheline

[Nick Piggin <nickpiggin@yahoo.com.au>]

Andrew Morton wrote:
> Nick Piggin <nickpiggin@yahoo.com.au> 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.