Re: [patch] mm: skip rebalance of hopeless zones

[Mel Gorman <mel@csn.ul.ie>]

On Wed, Dec 08, 2010 at 05:08:38PM -0800, Simon Kirby wrote:
> On Wed, Dec 08, 2010 at 07:49:03PM -0500, Rik van Riel wrote:
> 
> > On 12/08/2010 07:36 PM, Simon Kirby wrote:
> >
> >> Mel Gorman posted a similar patch to yours, but the logic is instead to
> >> consider order>0 balancing sufficient when there are other balanced zones
> >> totalling at least 25% of pages on this node.  This would probably fix
> >> your case as well.
> >
> > Mel's patch addresses something very different and is unlikely
> > to fix the problem this patch addresses.
> 
> Ok, I see they're quite separate.
> 
> Johannes' patch solves the problem of trying to balance a tiny Normal
> zone which happens to be full of unclaimable slab pages by giving up in
> this hopeless case, regardless of order.
> 
> Mel's patch solves the problem of fighting allocations causing an
> order>0 imbalance in the small Normal zone which happens to be full of
> reclaimable pages by giving up in this not-worth-bothering case.
> 
> The key difference is that Johannes' patch has no condition on order, so
> Mel's patch probably would help (though not for intended reasons) in the
> order != 0 case, and probably not in the order=0 case.
> 

I would be interested in hearing if the patch in that series that alters
how sleeping_prematurely() treats zone->all_unreclaimable makes a
difference though.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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