On (21/06/08 17:18), Christoph Lameter didst pronounce:
> On Sat, 21 Jun 2008, Mel Gorman wrote:
> 
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1249,15 +1249,13 @@ static unsigned long shrink_zone(int priority, 
> > struct zone *zone,
> >  static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
> >                                     struct scan_control *sc)
> >  {
> > +   enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
> >     unsigned long nr_reclaimed = 0;
> > -   struct zone **zones = zonelist->zones;
> > -   int i;
> > -
> > +   struct zone **z;
> > +   struct zone *zone;
> >  
> >     sc->all_unreclaimable = 1;
> > -   for (i = 0; zones[i] != NULL; i++) {
> > -           struct zone *zone = zones[i];
> > -
> > +   for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
> >             if (!populated_zone(zone))
> >                     continue;
> >             /*
> > 
> > Code before - Walk the zonelist for GFP_KERNEL
> 
> Before the change we walk all zones of the zonelist.
> 

Yeah, but the zonelist is for GFP_KERNEL so it should not include the HIGHMEM
zones, right? The key change is that after the patch there are fewer zonelists
than get filtered.

> > Code after - Filter zonelist based on what is allowed for GFP_KERNEL
> 
> After the change we walk only zones for GFP_KERNEL. Meaning no HIGHMEM 
> and MOVABLE zones. Doesnt that mean that reclaim is limited to ZONE_DMA 
> and ZONE_NORMAL? Is that really intended?
> 

It is for GFP_KERNEL allocations but that is expected.

> If not then the following patch should return us to old behavior:
> 

I think the effect of that patch is that zones get shrunk that have
nothing to do with the requestors requirements. Right?

> ---
>  mm/vmscan.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> Index: linux-2.6/mm/vmscan.c
> ===================================================================
> --- linux-2.6.orig/mm/vmscan.c        2008-06-21 17:15:45.597627317 -0700
> +++ linux-2.6/mm/vmscan.c     2008-06-21 17:17:16.273293260 -0700
> @@ -1249,13 +1249,12 @@ static unsigned long shrink_zone(int pri
>  static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
>                                       struct scan_control *sc)
>  {
> -     enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
>       unsigned long nr_reclaimed = 0;
>       struct zoneref *z;
>       struct zone *zone;
>  
>       sc->all_unreclaimable = 1;
> -     for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
> +     for_each_zone_zonelist(zone, z, zonelist, MAX_NR_ZONES - 1) {
>               if (!populated_zone(zone))
>                       continue;
>               /*
> 

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