Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent

From	Dou Liyang <douly.fnst@cn.fujitsu.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent
Date	2016-07-26 06:10 +0200
Message-ID	<rZ1QS-5E8-1@gated-at.bofh.it> (permalink)
References	<rYJAB-2kh-7@gated-at.bofh.it> <rYXtT-2Lh-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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在 2016年07月26日 07:20, Andrew Morton 写道:
> On Mon, 25 Jul 2016 16:35:42 +0800 Dou Liyang <douly.fnst@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.
>
> Plan B is to hunt down and fix up all the workqueue structures at
> hotplug-time.  Has that option been evaluated?
>

Yes, the option has been evaluate in this patch:
http://www.gossamer-threads.com/lists/linux/kernel/2116748

>
> Your fix is x86-only and this bug presumably affects other
> architectures, yes?I think a "Plan B" would fix all architectures?
>

Yes, the bug may presumably affect few architectures which support CPU 
hotplug and NUMA.

We have sent the "Plan B" in our community and got a lot of advice and 
ideas. Based on these suggestions, We carefully balance that two plan. 
Then we choice the first.

>
> Thirdly, what is the merge path for these patches?  Is an x86
> or ACPI maintainer working with you on them?

Yes, we get a lot of guidance and help from RJ who is an ACPI maintainer.


Thanks,

Dou

Thread

[PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  [PATCH v9 3/7] x86, acpi, cpu-hotplug: Introduce cpuid_to_apicid[] array to store persistent cpuid <-> apicid mapping. Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  [PATCH v9 4/7] x86, acpi, cpu-hotplug: Enable MADT APIs to return disabled apicid. Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  [PATCH v9 6/7] acpi: Provide the mechanism to validate processors in the ACPI tables Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  [PATCH v9 5/7] x86, acpi, cpu-hotplug: Set persistent cpuid <-> nodeid mapping when booting. Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  [PATCH v9 2/7] x86, acpi, cpu-hotplug: Enable acpi to register all possible cpus at boot time. Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-25 10:40 +0200
  Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Andrew Morton <akpm@linux-foundation.org> - 2016-07-26 01:30 +0200
    Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Tejun Heo <tj@kernel.org> - 2016-07-26 02:20 +0200
      Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Andrew Morton <akpm@linux-foundation.org> - 2016-07-26 02:30 +0200
        Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Tejun Heo <tj@kernel.org> - 2016-07-26 03:10 +0200
    Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-26 06:10 +0200
      Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-26 13:50 +0200
        Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent Dou Liyang <douly.fnst@cn.fujitsu.com> - 2016-07-27 03:20 +0200

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