On Tue, 2 Oct 2007 00:43:24 -0700
Andrew Morton <[email protected]> wrote:
> On Tue, 2 Oct 2007 16:36:24 +0900 KAMEZAWA Hiroyuki <[email protected]>
> > > Don't think so. A node is a lump of circuitry which can have zero or more
> > > CPUs, IO and memory.
> > >
> > > It may initially have been conceived as a memory-only concept in the Linux
> > > kernel, but that doesn't fully map onto reality (does it?)
> > >
> > > There was a real-world need for this, I think from the Fujitsu guys. That
> > > should be spelled out in the changelog but isn't.
> >
> > Yes, Fujitsu and HP guys really need this memory-less-node support.
> >
>
> For what reason, please?
>
For fujitsu, problem is called "empty" node.
When ACPI's SRAT table includes "possible nodes", ia64 bootstrap(acpi_numa_init)
creates nodes, which includes no memory, no cpu.
I tried to remove empty-node in past, but that was denied.
It was because we can hot-add cpu to the empty node.
(node-hotplug triggered by cpu is not implemented now. and it will be ugly.)
For HP, (Lee can comment on this later), they have memory-less-node.
As far as I hear, HP's machine can have following configration.
(example)
Node0: CPU0 memory AAA MB
Node1: CPU1 memory AAA MB
Node2: CPU2 memory AAA MB
Node3: CPU3 memory AAA MB
Node4: Memory XXX GB
AAA is very small value (below 16MB) and will be omitted by ia64 bootstrap.
After boot, only Node 4 has valid memory (but have no cpu.)
Maybe this is memory-interleave by firmware config.
Thanks,
-Kame
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