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SubjectRe: [RFC Patch V1 29/30] mm, x86: Enable memoryless node support to better support CPU/memory hotplug


On 2014/7/25 7:26, Nishanth Aravamudan wrote:
> On 11.07.2014 [15:37:46 +0800], Jiang Liu wrote:
>> With current implementation, all CPUs within a NUMA node will be
>> assocaited with another NUMA node if the node has no memory installed.
>
> <snip>
>
>> ---
>> arch/x86/Kconfig | 3 +++
>> arch/x86/kernel/acpi/boot.c | 5 ++++-
>> arch/x86/kernel/smpboot.c | 2 ++
>> arch/x86/mm/numa.c | 42 +++++++++++++++++++++++++++++++++++-------
>> 4 files changed, 44 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index a8f749ef0fdc..f35b25b88625 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1887,6 +1887,9 @@ config USE_PERCPU_NUMA_NODE_ID
>> def_bool y
>> depends on NUMA
>>
>> +config HAVE_MEMORYLESS_NODES
>> + def_bool NUMA
>> +
>> config ARCH_ENABLE_SPLIT_PMD_PTLOCK
>> def_bool y
>> depends on X86_64 || X86_PAE
>> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
>> index 86281ffb96d6..3b5641703a49 100644
>> --- a/arch/x86/kernel/acpi/boot.c
>> +++ b/arch/x86/kernel/acpi/boot.c
>> @@ -612,6 +612,8 @@ static void acpi_map_cpu2node(acpi_handle handle, int cpu, int physid)
>> if (nid != -1) {
>> set_apicid_to_node(physid, nid);
>> numa_set_node(cpu, nid);
>> + if (node_online(nid))
>> + set_cpu_numa_mem(cpu, local_memory_node(nid));
>
> How common is it for this method to be called for a CPU on an offline
> node? Aren't you fixing this in the next patch (so maybe the order
> should be changed?)?
Hi Nishanth,
For physical CPU hot-addition instead of logical CPU online through
sysfs, the node is always in offline state.
In v2, I have reordered the patch set so patch 30 goes first.

>
>> }
>> #endif
>> }
>> @@ -644,9 +646,10 @@ int acpi_unmap_lsapic(int cpu)
>> {
>> #ifdef CONFIG_ACPI_NUMA
>> set_apicid_to_node(per_cpu(x86_cpu_to_apicid, cpu), NUMA_NO_NODE);
>> + set_cpu_numa_mem(cpu, NUMA_NO_NODE);
>> #endif
>>
>> - per_cpu(x86_cpu_to_apicid, cpu) = -1;
>> + per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
>
> I think this is an unrelated change?
Thanks for reminder, it's unrelated to support memoryless node.

>
>> set_cpu_present(cpu, false);
>> num_processors--;
>>
>> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
>> index 5492798930ef..4a5437989ffe 100644
>> --- a/arch/x86/kernel/smpboot.c
>> +++ b/arch/x86/kernel/smpboot.c
>> @@ -162,6 +162,8 @@ static void smp_callin(void)
>> __func__, cpuid);
>> }
>>
>> + set_numa_mem(local_memory_node(cpu_to_node(cpuid)));
>> +
>
> Note that you might hit the same issue I reported on powerpc, if
> smp_callin() is part of smp_init(). The waitqueue initialization code
> depends on cpu_to_node() [and eventually cpu_to_mem()] to be initialized
> quite early.
Thanks for reminder. Patch 29/30 together will setup cpu_to_mem() array
when enumerating CPUs for hot-adding events, so it should be ready
for use when onlining those CPUs.

Regards!
Gerry
>
> Thanks,
> Nish
>


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