Re: [Bug 9941] New: Zone "Normal" missing in /proc/zoneinfo

[Andy Whitcroft <apw@shadowen.org>]

On Wed, Feb 13, 2008 at 11:52:25AM +0000, Mel Gorman wrote:

> > > > > $ grep zone /proc/zoneinfo
> > > > >
> > > > > Output with 2.6.24:
> > > > > Node 0, zone      DMA
> > > > > Node 0, zone    DMA32
> > > > > Node 0, zone   Normal
> > > > >
> > > > > Output with 2.6.24.2:
> > > > > Node 0, zone      DMA
> > > > > Node 0, zone    DMA32
> > > > >
> 
> The greater surprise to me is that "Normal" ever appeared. The zone is empty,
> why is information appearing about it? I checked the dmesg for an x86_64
> machine with 1GB of RAM that was running 2.6.24 here and there is no sign
> of Normal.
> 
> mel@arnold:/tmp$ grep zone zoneinfo.before 
> Node 0, zone      DMA
> Node 0, zone    DMA32
> 
> The loop looks like
> 
>         for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
>                 if (!populated_zone(zone))
>                         continue;
> 
> It makes no sense for it to show up *unless* 2.6.24 was compiled as a 32
> bit kernel by accident. Could this be the case?

Interestingly I would not expect to see DMA32 at all if the kernel was
compiled 32 bit as CONFIG_DMA32 defaults to X86_64.

Could we simply have less ram detected/present in this boot.  That would
make the zone dissappear if it became empty.

The e820 output as reported by the old and new kernels would confirm the
memory size is detected the same.  Also some idea of how much memory is
supposed be in the machine might shed some light.  If the overall is near
to 4GB it may be remapping for the AGP apature or something similar which
is shifting memory up above the boundary.

-apw

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