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Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE)

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> I also think that the kernel should commit to either zeroing the page
> or leaving it unchanged in response to MADV_FREE (even if the decision
> of which to do is made later on).  I think that your patch series does
> this, but only after a few of the patches are applied (the swap entry
> freeing), and I think that it should be a real guaranteed part of the
> semantics and maybe have a test case.

This would be a good thing to test because it would be required to add
MADV_FREE_UNDO down the road. It would mean the same semantics as the
MEM_RESET and MEM_RESET_UNDO features on Windows, and there's probably
value in that for the sake of migrating existing software too.

For one example, it could be dropped into Firefox:

https://dxr.mozilla.org/mozilla-central/source/memory/volatile/VolatileBufferWindows.cpp

And in Chromium:

https://code.google.com/p/chromium/codesearch#chromium/src/base/memory/discardable_shared_memory.cc

Worth noting that both also support the API for pinning/unpinning that's
used by Android's ashmem too. Linux really needs a feature like this for
caches. Firefox simply doesn't drop the memory at all on Linux right now:

https://dxr.mozilla.org/mozilla-central/source/memory/volatile/VolatileBufferFallback.cpp

(Lock == pin, Unlock == unpin)

For reference:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa366887(v=vs.85).aspx

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[PATCH v3 00/17] MADFV_FREE support Minchan Kim <minchan@kernel.org> - 2015-11-12 05:40 +0100
  [PATCH v3 08/17] x86: add pmd_[dirty|mkclean] for THP Minchan Kim <minchan@kernel.org> - 2015-11-12 05:40 +0100
  [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-12 05:40 +0100
    Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Andy Lutomirski <luto@amacapital.net> - 2015-11-12 06:00 +0100
      Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Daniel Micay <danielmicay@gmail.com> - 2015-11-12 06:30 +0100
        Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-13 07:20 +0100
          Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Daniel Micay <danielmicay@gmail.com> - 2015-11-13 07:20 +0100
            Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-13 07:40 +0100
              Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Daniel Micay <danielmicay@gmail.com> - 2015-11-13 07:50 +0100
                Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-13 08:10 +0100
                Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Daniel Micay <danielmicay@gmail.com> - 2015-11-13 09:20 +0100
                Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Andy Lutomirski <luto@amacapital.net> - 2015-11-13 20:50 +0100
                Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-16 03:20 +0100
                Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) yalin wang <yalin.wang2010@gmail.com> - 2015-11-16 04:20 +0100
    Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-11-12 12:30 +0100
      Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Minchan Kim <minchan@kernel.org> - 2015-11-13 07:20 +0100
  [PATCH v3 11/17] arm: add pmd_mkclean for THP Minchan Kim <minchan@kernel.org> - 2015-11-12 05:40 +0100

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