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SubjectRe: [PATCH v3 0/5] Make cpuid <-> nodeid mapping persistent.
Hi Ishimatsu,

On 12/10/2015 05:10 AM, Yasuaki Ishimatsu wrote:
> Hi Tang,
>
> I applied your patches into linux-4.4.0-rc4 and tried to boot up
> the system with mem= boot option, but system does not boot up.
> Unfortunately boot messages were not shown. So I cannot find out
> the reason.

Thank you for testing. And yes, it failed to boot too early.
I'm working on it.

>
> The reason of using the mem= boot option is to limit memory and
> create memoryless node on purpose since your patches support
> memoryless node.
>
> Here is an example method to create memoryless node on purpose.
>
> My box has the following SRAT:
>
> SRAT: Node 0 PXM 0 [mem 0x00000000-0x5fffffff]
> SRAT: Node 0 PXM 0 [mem 0x100000000-0x109fffffff]
> SRAT: Node 1 PXM 1 [mem 0x10a0000000-0x209fffffff]
> SRAT: Node 2 PXM 2 [mem 0x20a0000000-0x309fffffff]
> SRAT: Node 3 PXM 3 [mem 0x30a0000000-0x409fffffff]
>
> So when booting up the system with mem=0x20a0000000, Memory of
> Node 2 and 3 are ignored and the Nodes become memoryless node.

OK, I'm using initrd overwrite. It could also fake the memory-less node.

Thanks.

>
> Thanks,
> Yasuaki Ishimatsu
> On Thu, 19 Nov 2015 12:22:10 +0800
> Tang Chen <tangchen@cn.fujitsu.com> wrote:
>
>> [Problem]
>>
>> cpuid <-> nodeid mapping is firstly established at boot time. And workqueue caches
>> the mapping in wq_numa_possible_cpumask in wq_numa_init() at boot time.
>>
>> When doing node online/offline, cpuid <-> nodeid mapping is established/destroyed,
>> which means, cpuid <-> nodeid mapping will change if node hotplug happens. But
>> workqueue does not update wq_numa_possible_cpumask.
>>
>> So here is the problem:
>>
>> Assume we have the following cpuid <-> nodeid in the beginning:
>>
>> Node | CPU
>> ------------------------
>> node 0 | 0-14, 60-74
>> node 1 | 15-29, 75-89
>> node 2 | 30-44, 90-104
>> node 3 | 45-59, 105-119
>>
>> and we hot-remove node2 and node3, it becomes:
>>
>> Node | CPU
>> ------------------------
>> node 0 | 0-14, 60-74
>> node 1 | 15-29, 75-89
>>
>> and we hot-add node4 and node5, it becomes:
>>
>> Node | CPU
>> ------------------------
>> node 0 | 0-14, 60-74
>> node 1 | 15-29, 75-89
>> node 4 | 30-59
>> node 5 | 90-119
>>
>> But in wq_numa_possible_cpumask, cpu30 is still mapped to node2, and the like.
>>
>> When a pool workqueue is initialized, if its cpumask belongs to a node, its
>> pool->node will be mapped to that node. And memory used by this workqueue will
>> also be allocated on that node.
>>
>> static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs){
>> ...
>> /* if cpumask is contained inside a NUMA node, we belong to that node */
>> if (wq_numa_enabled) {
>> for_each_node(node) {
>> if (cpumask_subset(pool->attrs->cpumask,
>> wq_numa_possible_cpumask[node])) {
>> pool->node = node;
>> break;
>> }
>> }
>> }
>>
>> Since wq_numa_possible_cpumask is not updated, it could be mapped to an offline node,
>> which will lead to memory allocation failure:
>>
>> SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
>> cache: kmalloc-192, object size: 192, buffer size: 192, default order: 1, min order: 0
>> node 0: slabs: 6172, objs: 259224, free: 245741
>> node 1: slabs: 3261, objs: 136962, free: 127656
>>
>> It happens here:
>>
>> create_worker(struct worker_pool *pool)
>> |--> worker = alloc_worker(pool->node);
>>
>> static struct worker *alloc_worker(int node)
>> {
>> struct worker *worker;
>>
>> worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); --> Here, useing the wrong node.
>>
>> ......
>>
>> return worker;
>> }
>>
>>
>> [Solution]
>>
>> There are four mappings in the kernel:
>> 1. nodeid (logical node id) <-> pxm
>> 2. apicid (physical cpu id) <-> nodeid
>> 3. cpuid (logical cpu id) <-> apicid
>> 4. cpuid (logical cpu id) <-> nodeid
>>
>> 1. pxm (proximity domain) is provided by ACPI firmware in SRAT, and nodeid <-> pxm
>> mapping is setup at boot time. This mapping is persistent, won't change.
>>
>> 2. apicid <-> nodeid mapping is setup using info in 1. The mapping is setup at boot
>> time and CPU hotadd time, and cleared at CPU hotremove time. This mapping is also
>> persistent.
>>
>> 3. cpuid <-> apicid mapping is setup at boot time and CPU hotadd time. cpuid is
>> allocated, lower ids first, and released at CPU hotremove time, reused for other
>> hotadded CPUs. So this mapping is not persistent.
>>
>> 4. cpuid <-> nodeid mapping is also setup at boot time and CPU hotadd time, and
>> cleared at CPU hotremove time. As a result of 3, this mapping is not persistent.
>>
>> To fix this problem, we establish cpuid <-> nodeid mapping for all the possible
>> cpus at boot time, and make it persistent. And according to init_cpu_to_node(),
>> cpuid <-> nodeid mapping is based on apicid <-> nodeid mapping and cpuid <-> apicid
>> mapping. So the key point is obtaining all cpus' apicid.
>>
>> apicid can be obtained by _MAT (Multiple APIC Table Entry) method or found in
>> MADT (Multiple APIC Description Table). So we finish the job in the following steps:
>>
>> 1. Enable apic registeration flow to handle both enabled and disabled cpus.
>> This is done by introducing an extra parameter to generic_processor_info to let the
>> caller control if disabled cpus are ignored.
>>
>> 2. Introduce a new array storing all possible cpuid <-> apicid mapping. And also modify
>> the way cpuid is calculated. Establish all possible cpuid <-> apicid mapping when
>> registering local apic. Store the mapping in this array.
>>
>> 3. Enable _MAT and MADT relative apis to return non-presnet or disabled cpus' apicid.
>> This is also done by introducing an extra parameter to these apis to let the caller
>> control if disabled cpus are ignored.
>>
>> 4. Establish all possible cpuid <-> nodeid mapping.
>> This is done via an additional acpi namespace walk for processors.
>>
>>
>> For previous discussion, please refer to:
>> https://lkml.org/lkml/2015/2/27/145
>> https://lkml.org/lkml/2015/3/25/989
>> https://lkml.org/lkml/2015/5/14/244
>> https://lkml.org/lkml/2015/7/7/200
>> https://lkml.org/lkml/2015/9/27/209
>>
>>
>> Change log v2 -> v3:
>> 1. Online memory-less nodes at boot time to map cpus of memory-less nodes.
>> 2. Build zonelists for memory-less nodes so that memory allocator will fall
>> back to proper nodes automatically.
>>
>> Change log v1 -> v2:
>> 1. Split code movement and actual changes. Add patch 1.
>> 2. Synchronize best near online node record when node hotplug happens. In patch 2.
>> 3. Fix some comment.
>>
>>
>> Gu Zheng (4):
>> x86, acpi, cpu-hotplug: Enable acpi to register all possible cpus at
>> boot time.
>> x86, acpi, cpu-hotplug: Introduce cpuid_to_apicid[] array to store
>> persistent cpuid <-> apicid mapping.
>> x86, acpi, cpu-hotplug: Enable MADT APIs to return disabled apicid.
>> x86, acpi, cpu-hotplug: Set persistent cpuid <-> nodeid mapping when
>> booting.
>>
>> Tang Chen (1):
>> x86, memhp, numa: Online memory-less nodes at boot time.
>>
>> arch/ia64/kernel/acpi.c | 2 +-
>> arch/x86/include/asm/mpspec.h | 1 +
>> arch/x86/kernel/acpi/boot.c | 8 ++-
>> arch/x86/kernel/apic/apic.c | 85 +++++++++++++++++++++++++----
>> arch/x86/mm/numa.c | 30 ++++++-----
>> drivers/acpi/acpi_processor.c | 5 +-
>> drivers/acpi/bus.c | 3 ++
>> drivers/acpi/processor_core.c | 122 ++++++++++++++++++++++++++++++++++--------
>> include/linux/acpi.h | 2 +
>> include/linux/mmzone.h | 1 +
>> mm/page_alloc.c | 2 +-
>> 11 files changed, 209 insertions(+), 52 deletions(-)
>>
>> --
>> 1.8.3.1
>>
>
> .
>





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