On Fri, 2010-05-21 at 17:12 +0800, minskey guo wrote:
> 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:
> >>
> >> numa-slab-use-numa_mem_id-for-slab-local-memory-node.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);
> >> ...
> >>
> >> +#ifdef CONFIG_HAVE_MEMORYLESS_NODES
> >> + if (cpu_online(cpu))
> >> + cpu_to_mem(cpu) = local_memory_node(cpu_to_node(cpu));
> >> +#endif
>
> 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 ?
Minskey:
As I mentioned to Kame-san, x86 does not define
CONFIG_HAVE_MEMORYLESS_NODES, so this code is not compiled for that
arch. If x86 did support memoryless nodes--i.e., did not hide them and
reassign the cpus to other nodes, as is the case for ia64--then we could
have on-line cpus associated with memoryless nodes. The code above is
in __build_all_zonelists() so that in the case where we add memory to a
previously memoryless node, we re-evaluate the "local memory node" for
all online cpus.
For cpu hotplug--again, if x86 supports memoryless nodes--we'll need to
add a similar chunk to the path where we set up the cpu_to_node map for
a hotplugged cpu. See, for example, the call to set_numa_mem() in
smp_callin() in arch/ia64/kernel/smpboot.c. But currently, I don't
think you can use the numa_mem_id()/cpu_to_mem() interfaces for your
purpose. I suppose you could change page_alloc.c to compile
local_memory_node() #if defined(CONFIG_HAVE_MEMORYLESS_NODES) || defined
(CPU_HOTPLUG) and use that function to find the nearest memory. It
should return a valid node after zonelists have been rebuilt.
Does that make sense?
Lee
>
>
> >
> > 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.
>
>
> -minskey
>
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