Re: NUMA API for Linux

["Martin J. Bligh" <mbligh@aracnet.com>]

> On Wed, 7 Apr 2004, Andrew Morton wrote:
>> 
>> Your patch takes the CONFIG_NUMA vma from 64 bytes to 68.  It would be nice
>> to pull those 4 bytes back somehow.
> 
> How significant is this vma size issue?
> 
> anon_vma objrmap will add 20 bytes to each vma (on 32-bit arches):
> 8 for prio_tree, 12 for anon_vma linkage in vma,
> sometimes another 12 for the anon_vma head itself.

Ewwww. Isn't some of that shared most of the time though?

> anonmm objrmap adds just the 8 bytes for prio_tree,
> remaining overhead 28 bytes per mm.

28 bytes per *mm* is nothing, and I still think the prio_tree is 
completely unneccesary. Nobody has ever demonstrated a real benchmark
that needs it, as far as I recall.

> Seems hard on Andi to begrudge him 4.

I don't care about the 4 bytes much (other than that the current 64 happens
to be a nice size). I just don't see the point in making copies of the 
binding structure all the time ;-) Refcounts aren't that hard ... didn't
Greg do a kref just recently? ...

M.