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Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field

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On Tue, Jul 4, 2017 at 10:51 PM, Michal Hocko <mhocko@kernel.org> wrote:
> On Mon 03-07-17 17:14:14, Jérôme Glisse wrote:
>> HMM pages (private or public device pages) are ZONE_DEVICE page and
>> thus you can not use page->lru fields of those pages. This patch
>> re-arrange the uncharge to allow single page to be uncharge without
>> modifying the lru field of the struct page.
>>
>> There is no change to memcontrol logic, it is the same as it was
>> before this patch.
>
> What is the memcg semantic of the memory? Why is it even charged? AFAIR
> this is not a reclaimable memory. If yes how are we going to deal with
> memory limits? What should happen if go OOM? Does killing an process
> actually help to release that memory? Isn't it pinned by a device?
>
> For the patch itself. It is quite ugly but I haven't spotted anything
> obviously wrong with it. It is the memcg semantic with this class of
> memory which makes me worried.
>

This is the HMM CDM case. Memory is normally malloc'd and then
migrated to ZONE_DEVICE or vice-versa. One of the things we did
discuss was seeing ZONE_DEVICE memory in user page tables.

Balbir Singh.

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[PATCH 0/5] Cache coherent device memory (CDM) with HMM v3 Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200
  [PATCH 5/5] mm/memcontrol: support MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_PUBLIC Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200
  [PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2 Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200
    Re: [PATCH 2/5] mm/device-public-memory: device memory cache  coherent with CPU v2 Balbir Singh <bsingharora@gmail.com> - 2017-07-11 06:20 +0200
      Re: [PATCH 2/5] mm/device-public-memory: device memory cache  coherent with CPU v2 Jerome Glisse <jglisse@redhat.com> - 2017-07-11 17:00 +0200
        Re: [PATCH 2/5] mm/device-public-memory: device memory cache  coherent with CPU v2 Balbir Singh <bsingharora@gmail.com> - 2017-07-12 08:00 +0200
  [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum memory_type one Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200
    Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Dan Williams <dan.j.williams@intel.com> - 2017-07-04 01:50 +0200
      Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Jerome Glisse <jglisse@redhat.com> - 2017-07-05 16:30 +0200
        Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Dan Williams <dan.j.williams@intel.com> - 2017-07-05 18:20 +0200
          Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Jerome Glisse <jglisse@redhat.com> - 2017-07-05 20:50 +0200
            Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and  enum memory_type one Balbir Singh <bsingharora@gmail.com> - 2017-07-11 05:50 +0200
            Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Dan Williams <dan.j.williams@intel.com> - 2017-07-11 09:40 +0200
              Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Jerome Glisse <jglisse@redhat.com> - 2017-07-11 17:10 +0200
                Re: [PATCH 1/5] mm/persistent-memory: match IORES_DESC name and enum  memory_type one Dan Williams <dan.j.williams@intel.com> - 2017-07-11 19:00 +0200
  [PATCH 4/5] mm/memcontrol: allow to uncharge page without using page->lru field Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200
    Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-04 15:00 +0200
      Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Balbir Singh <bsingharora@gmail.com> - 2017-07-05 05:20 +0200
        Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-05 08:40 +0200
          Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Balbir Singh <bsingharora@gmail.com> - 2017-07-05 12:30 +0200
      Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Jerome Glisse <jglisse@redhat.com> - 2017-07-05 16:40 +0200
        Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-10 10:30 +0200
          Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Jerome Glisse <jglisse@redhat.com> - 2017-07-10 17:40 +0200
            Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-10 18:10 +0200
              Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Jerome Glisse <jglisse@redhat.com> - 2017-07-10 18:30 +0200
                Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-10 18:40 +0200
                Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Jerome Glisse <jglisse@redhat.com> - 2017-07-10 19:00 +0200
                Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Michal Hocko <mhocko@kernel.org> - 2017-07-10 19:50 +0200
                Re: [PATCH 4/5] mm/memcontrol: allow to uncharge page without using  page->lru field Jerome Glisse <jglisse@redhat.com> - 2017-07-10 20:20 +0200
  [PATCH 3/5] mm/hmm: add new helper to hotplug CDM memory region Jérôme Glisse <jglisse@redhat.com> - 2017-07-03 23:20 +0200

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