Re: [2.6.20][PATCH] fix mempolicy error check on a system with memory-less-node

Andrew Morton
2007-02-07T17:43:53Z

On Wed, 7 Feb 2007 17:50:55 +0100 Andi Kleen <ak@suse.de> wrote:

> On Wednesday 07 February 2007 17:23, Andrew Morton wrote:
> > On 07 Feb 2007 11:20:06 +0100 Andi Kleen <ak@suse.de> wrote:
> >
> > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> writes:
> > >
> > > > current mempolicy just checks whether a node is online or not.
> > > > If there is memory-less-node, mempolicy's target node can be
> > > > invalid.
> > > > This patch adds a check whether a node has memory or not.
> > >
> > > IMHO there shouldn't be any memory less nodes. The architecture code
> > > should not create them. The CPU should be assigned to a nearby node instead.
> >
> > umm, why?
> >
> > A node which has CPUs and no memory is obviously physically possible and
> > isn't a completely insane thing for a user to do. I'd have thought that
> > the kernel should be able to cleanly and clearly handle it,
>
> It doesn't.

Fix it?

> > and to
> > accurately present the machine's topology to the user without us having to
> > go adding falsehoods like this?
>
> a node is a piece of memory. Without memory it doesn't make sense.

Who said? I can pick up a piece of circuitry which has four CPUs and no
RAM, wave it about then stick it in a computer. The kernel is just wrong,
surely?