Re: NUMA API for Linux

[Andrew Morton]

Hugh Dickins <hugh@xxxxxxxxxxx> wrote:
>
> 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?

For some workloads/machines it will simply cause an
approximately-proportional reduction in the size of the workload which we
can handle.

ie: there are some (oracle) workloads where the kernel craps out due to
lowmem vma exhaustion.  If they're now using remap_file_pages() for this then
it may not be a problem any more.  Ingo would know better than I.

> 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.
> 
> anonmm objrmap adds just the 8 bytes for prio_tree,
> remaining overhead 28 bytes per mm.
> 
> Seems hard on Andi to begrudge him 4.

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