Messages in this thread | | | Date | Tue, 11 Jul 2006 15:55:38 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] remove empty node at boot time |
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On Mon, 10 Jul 2006 11:03:03 -0600 Bjorn Helgaas <bjorn.helgaas@hp.com> wrote:
> On Sunday 09 July 2006 23:19, KAMEZAWA Hiroyuki wrote: > > Could you try this patch ? (against 2.6.18-rc1) > > Your patch does fix it. But I'm worried about removing > empty nodes at boot-time. I want to support the following > scenario: > > node 0: 1 enabled CPU, 3 disabled CPUs, no local memory > node 1: 4 disabled CPUs, no local memory > node 2: no CPUs, big interleaved memory across nodes 0 & 1 > > At run-time, I'd like to be able to enable any or all of the > 7 disabled CPUs. If you remove the "empty" node 1 at boot-time, > it sounds like I won't be able to enable its CPUs later. >
Hmm.. in my understanding, all structures for *possible* cpus are allocated at boot time. Then, only problem seems that a cpu is tied to not-exisiting-node at boot time. (see arch/ia64/kernel/numa.c, build_cpu_to_node_map())
==== void __init build_cpu_to_node_map(void) { int cpu, i, node;
for(node=0; node < MAX_NUMNODES; node++) cpus_clear(node_to_cpu_mask[node]);
for(cpu = 0; cpu < NR_CPUS; ++cpu) { node = -1; for (i = 0; i < NR_CPUS; ++i) if (cpu_physical_id(cpu) == node_cpuid[i].phys_id) { node = node_cpuid[i].nid; break; } cpu_to_node_map[cpu] = (node >= 0) ? node : 0; if (node >= 0) cpu_set(cpu, node_to_cpu_mask[node]); } } =====
Then what we have to do here are 1. remap cpu to the first existing node at hot-add event or 2. implement node-hot-add triggered by cpu-hot-add. Because we already have implemented node-hot-add triggered by memory-hotadd we can do it by small effort.
I think above will work for your environment. do you have any idea other than "don't remove empty node at boot time" ? or reserve empty node is the best way ?
- Kame
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