Messages in this thread | | | Date | Mon, 11 May 2009 12:27:49 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH 3/3] x86: fix node_possible_map logic -v2 |
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On Mon, 11 May 2009, Jack Steiner wrote:
> Do we have a clear and unambiguous definition of what a node really is? > In this case, is a board (socket) with cpus, a unique PXM but no memory > considered a node. Even though it has no memory, it is a node (depending on the > definition of "node") for purposes such as scheduling. The memoryless node also > has local IO buses that want to direct interrupts to node-local cpus. >
In your example of two cpus (0-1) that are remote to the system's only memory and two cpus (2-3) that have affinity to that memory, it appears as though the kernel is considering cpus 2-3 and the memory to be a node and cpus 0-1 to be a memoryless node.
That's a pretty useless scenario for memoryless node support, actually, unless there's a third node with memory that cpus 0-1 have a different distance to. cpus 0-1 have no memory that is local, so the "remote" memory should be considered local to them.
I don't know who has been pushing the memoryless node support, but it appears as though it hasn't been fully tested yet. The NULL pglist_data here for node 0 seems appropriate since you don't need it unless you're describing memory, but the kernel implies that if a bit is set in node_online_map or node_possible_map that it has this associated data.
Added Andi Kleen to the cc list.
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