Messages in this thread | | | Subject | Re: [PATCH v9 0/7] Make cpuid <-> nodeid mapping persistent | From | Dou Liyang <> | Date | Wed, 27 Jul 2016 09:18:19 +0800 |
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Hi, RJ
在 2016年07月26日 19:53, Rafael J. Wysocki 写道: > On Tuesday, July 26, 2016 11:59:38 AM Dou Liyang wrote: >> >> 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. > > FWIW, the patches are fine by me from the ACPI perspective. > > If you want me to apply them, though, ACKs from the x86 and mm maintainers > will be necessary. >
I will continue to investigate this bug and wait for maintainers's advices.
> Thanks, > Rafael > > >
Thanks. Dou
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