From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Wed, 18 Feb 2004 19:13:59 +0000 Subject: Re: PXM/Nid/SLIT patch Message-Id: <20040218191359.A11957@infradead.org> List-Id: References: <40321CF7.5020301@hp.com> In-Reply-To: <40321CF7.5020301@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Wed, Feb 18, 2004 at 10:59:03AM -0800, David Mosberger wrote: > This comment concerns me. I certainly have always tried to judge > patches based on their technical merits for Linux. Is there anything > in particular that I did (or didn't) do that you found objectionable? > If so, please let me know. Nah, this wasn't meant as an attac against you, it's just that HP seems to do most of the work and thus everything in arch/ia64/ is a little HP centric. I guess it'll change by the time now that SGI woke up a little. > Hmmh, I'm no NUMA-expert and it isn't clear to me whether the patch is > working around a firmware-bug or a limitation in the Linux NUMA code. > I don't see off-hand why it should be illegal to have a memory config > with only one node with memory. The whole PXM_MAGIC business looks > strange to me though. Can someone explain? There's two issues. First we should probably handle CPU-less nodes, but that's not what this patch does. The second issue is that the firmware reports plain wrong data to work around the lack of NUMA support in a certain legacy OS from Redmond, and I don't think we should so this non-standard workaround in Linux for that. Robert's idea of a switch in the firmware to report proper tables sounds like the best way to go, maybe together with a fix to allow cpu-less nodes to allow boxes with old firmware to boot, even with suboptimal performance.