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Re: [PATCH v5 RESEND 0/5] Make cpuid <-> nodeid mapping persistent

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  Re: [PATCH v5 RESEND 0/5] Make cpuid <-> nodeid mapping persistent Zhu Guihua <zhugh.fnst@cn.fujitsu.com> - 2016-02-03 10:30 +0100
    Re: [PATCH v5 RESEND 0/5] Make cpuid <-> nodeid mapping persistent "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-03 13:10 +0100
      Re: [PATCH v5 RESEND 0/5] Make cpuid <-> nodeid mapping persistent Tejun Heo <tj@kernel.org> - 2016-02-03 17:50 +0100

#1325081 — Re: [PATCH v5 RESEND 0/5] Make cpuid <-> nodeid mapping persistent

On 01/25/2016 02:12 PM, Tang Chen wrote:
> Hi Rafael, Len,
>
> Would you please help to review the ACPI part of this patch-set ?

Can anyone help to review this?

Cc tj:
Can you add acked-by into this patchset?

Thanks.
>
> Thanks.
>
> On 01/25/2016 02:08 PM, Tang Chen 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 v4 -> v5:
>> 1. Remove useless code in patch 1.
>> 2. Small improvement of commit message.
>>
>> Change log v3 -> v4:
>> 1. Fix the kernel panic at boot time. The cause is that I tried to 
>> build zonelists
>>     before per cpu areas were initialized.
>>
>> 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            |  27 +++++-----
>>   drivers/acpi/acpi_processor.c |   5 +-
>>   drivers/acpi/bus.c            |   3 ++
>>   drivers/acpi/processor_core.c | 122 
>> ++++++++++++++++++++++++++++++++++--------
>>   include/linux/acpi.h          |   2 +
>>   9 files changed, 204 insertions(+), 51 deletions(-)
>>
>
>
>
> .
>

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#1325319

Hi,

On Wed, Feb 3, 2016 at 10:14 AM, Zhu Guihua <zhugh.fnst@cn.fujitsu.com> wrote:
>
> On 01/25/2016 02:12 PM, Tang Chen wrote:
>>
>> Hi Rafael, Len,
>>
>> Would you please help to review the ACPI part of this patch-set ?
>
>
> Can anyone help to review this?

I'm planning to look into this more thoroughly in the next few days.

Thanks,
Rafael

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#1325671

Hello,

This also made workqueue blow up when delayed modding races cpu
offlining.

 http://lkml.kernel.org/g/1454424264.11183.46.camel@gmail.com

I'll work around it from the queueing path but it'd be great if the
mapping can be made stable sooner than later.

Thanks.

-- 
tejun

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