Re: [PATCH] online CPU before memory failed in pcpu_alloc_pages()

From: minskey guo
Date: Fri May 21 2010 - 05:13:00 EST

On 05/21/2010 04:39 PM, KAMEZAWA Hiroyuki wrote:
On Fri, 21 May 2010 16:22:19 +0800
minskey guo<chaohong_guo@xxxxxxxxxxxxxxx> wrote:

Yes. I can use cpu_to_mem(). only some little difference during
CPU online: 1st cpu within memoryless node gets memory from current
node or the node to which the cpu0 belongs,

But I have a question about the patch:


@@ -2968,9 +2991,23 @@ static int __build_all_zonelists(void *d

- for_each_possible_cpu(cpu)
+ for_each_possible_cpu(cpu) {
setup_pageset(&per_cpu(boot_pageset, cpu), 0);

+ if (cpu_online(cpu))
+ cpu_to_mem(cpu) = local_memory_node(cpu_to_node(cpu));

Look at the above code, int __build_all_zonelists(), cpu_to_mem(cpu)
is set only when cpu is onlined. Suppose that a node with local memory,
all memory segments are onlined first, and then, cpus within that node
are onlined one by one, in this case, where does the cpu_to_mem(cpu)
for the last cpu get its value ?

So, cpu_to_node(cpu) for possible cpus will have NUMA_NO_NODE(-1)
or the number of the nearest node.

IIUC, if SRAT is not broken, all pxm has its own node_id.

Thank you very much for the info, I have been thinking why node_id
is (-1) in some cases.

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