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Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory"

From Dan Williams <dan.j.williams@intel.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory"
Date 2015-08-15 00:40 +0200
Message-ID <pXvNL-7b2-1@gated-at.bofh.it> (permalink)
References <pWRQl-8uz-3@gated-at.bofh.it> <pWRQl-8uz-1@gated-at.bofh.it> <pXuRI-5Qe-17@gated-at.bofh.it> <pXvb3-6cV-3@gated-at.bofh.it> <pXvkJ-6Dt-13@gated-at.bofh.it>
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On Fri, Aug 14, 2015 at 3:06 PM, Jerome Glisse <j.glisse@gmail.com> wrote:
> On Fri, Aug 14, 2015 at 02:52:15PM -0700, Dan Williams wrote:
>> On Fri, Aug 14, 2015 at 2:37 PM, Jerome Glisse <j.glisse@gmail.com> wrote:
>> > On Wed, Aug 12, 2015 at 11:50:05PM -0400, Dan Williams wrote:
[..]
>> > What is the rational for not updating max_pfn, max_low_pfn, ... ?
>> >
>>
>> The idea is that this memory is not meant to be available to the page
>> allocator and should not count as new memory capacity.  We're only
>> hotplugging it to get struct page coverage.
>
> But this sounds bogus to me to rely on max_pfn to stay smaller than
> first_dev_pfn.  For instance you might plug a device that register
> dev memory and then some regular memory might be hotplug, effectively
> updating max_pfn to a value bigger than first_dev_pfn.
>

True.

> Also i do not think that the buddy allocator use max_pfn or max_low_pfn
> to consider page/zone for allocation or not.

Yes, I took it out with no effects.  I'll investigate further whether
we should be touching those variables or not for this new usage.
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Thread

[RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-13 06:00 +0200
  Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Jerome Glisse <j.glisse@gmail.com> - 2015-08-14 23:40 +0200
    Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-15 00:00 +0200
      Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Jerome Glisse <j.glisse@gmail.com> - 2015-08-15 00:10 +0200
        Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-15 00:40 +0200
          Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-15 04:20 +0200
            Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Jerome Glisse <j.glisse@gmail.com> - 2015-08-17 23:50 +0200
              Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-18 02:50 +0200
                Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Jerome Glisse <j.glisse@gmail.com> - 2015-08-18 19:00 +0200
                Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Dan Williams <dan.j.williams@intel.com> - 2015-08-18 19:30 +0200
                Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Jerome Glisse <j.glisse@gmail.com> - 2015-08-18 21:10 +0200
      Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Christoph Hellwig <hch@lst.de> - 2015-08-15 11:10 +0200
  Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" Christoph Hellwig <hch@lst.de> - 2015-08-15 15:40 +0200

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