Re: [PATCH 14/14] page-replace-kswapd-incmin.patch

Peter Zijlstra
2005-12-31T09:40:40Z

On Fri, 2005-12-30 at 23:15 -0200, Marcelo Tosatti wrote:
> On Fri, Dec 30, 2005 at 11:42:34PM +0100, Peter Zijlstra wrote:
> >
> > From: Nick Piggin <npiggin@suse.de>
> >
> > Explicitly teach kswapd about the incremental min logic instead of just scanning
> > all zones under the first low zone. This should keep more even pressure applied
> > on the zones.
> >
> > The new shrink_zone() logic exposes the very worst side of the current
> > balance_pgdat() function. Without this patch reclaim is limited to ZONE_DMA.
>
> Can you please describe the issue with over protection of DMA zone you experienced?
>
> I'll see if I can reproduce it with Nick's standalone patch on top of vanilla, what
> load was that?

With the mdb bench the following behaviour was observed:
(mem=128M)

- PageCache would fill zone_normal
- PageCache would fill zone_dma
- reclaim starts
- initially things look right
- after a while zone_dma is reclaimed so fast that it frequently gets a
full eviction (nr_resident == 0).
- from this point onward zone_normal practiaclly sits idle and zone_dma
goes wild with all the action.

--
Peter Zijlstra <a.p.zijlstra@chello.nl>