Re: [patch 09/18] SLUB: Trigger defragmentation from memory reclaim

[Christoph Lameter <clameter@sgi.com>]

On Mon, 7 Apr 2008, Andrew Morton wrote:

> > + * zone is the zone for which we are shrinking the slabs. If the intent
> > + * is to do a global shrink then zone may be NULL. Specification of a
> > + * zone is currently only used to limit slab defragmentation to a NUMA node.
> > + * The performace of shrink_slab would be better (in particular under NUMA)
> > + * if it could be targeted as a whole to the zone that is under memory
> > + * pressure but the VFS infrastructure does not allow that at the present
> > + * time.
> 
> Surely this will falsely trigger the ->next_defrag logic?

slab reclaim is run rarely so I thought that these races do not matter 
much.

We could put that next_defrag logic into the per node structure 
and protect it by taking the partial list lock if we wanted to be race 
safe.

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