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Groups > linux.kernel > #1204299

Re: page-flags behavior on compound pages: a worry

From Christoph Lameter <cl@linux.com>
Newsgroups linux.kernel
Subject Re: page-flags behavior on compound pages: a worry
Date 2015-08-10 16:00 +0200
Message-ID <pVVMm-88D-27@gated-at.bofh.it> (permalink)
References (4 earlier) <pUz1w-1yi-9@gated-at.bofh.it> <pUAgZ-3gz-59@gated-at.bofh.it> <pURhN-2CP-45@gated-at.bofh.it> <pURKO-3vi-19@gated-at.bofh.it> <pVThw-4Hc-9@gated-at.bofh.it>
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On Mon, 10 Aug 2015, Kirill A. Shutemov wrote:

> I don't see anything actionable here. Your wish list doesn't cope with
> reality. Compound pages are mapped with PTEs for almost ten years and I
> don't see why we should stop the practice.

Well they have to if they are smaller than huge pages. Treating each PTE
as each having their own state instead of having the whole compound mapped
completely causes the problem. Refcounting in tail pages is not necessary
if the whole compound is either mapped or not mapped at all by a process.
Refcounting in tail pages is only necessary if you allow 4k slices to be
mapped.

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Thread

page-flags behavior on compound pages: a worry Hugh Dickins <hughd@google.com> - 2015-08-06 06:20 +0200
  Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-06 17:40 +0200
    Re: page-flags behavior on compound pages: a worry Hugh Dickins <hughd@google.com> - 2015-08-06 21:30 +0200
      Re: page-flags behavior on compound pages: a worry Christoph Lameter <cl@linux.com> - 2015-08-06 22:50 +0200
        Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-07 17:00 +0200
          Re: page-flags behavior on compound pages: a worry Christoph Lameter <cl@linux.com> - 2015-08-07 17:30 +0200
            Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-10 13:20 +0200
              Re: page-flags behavior on compound pages: a worry Christoph Lameter <cl@linux.com> - 2015-08-10 16:00 +0200
      Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-07 17:00 +0200
        Re: page-flags behavior on compound pages: a worry Hugh Dickins <hughd@google.com> - 2015-08-13 07:20 +0200
      Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-12 16:40 +0200
        Re: page-flags behavior on compound pages: a worry Vlastimil Babka <vbabka@suse.cz> - 2015-08-12 16:50 +0200
        Re: page-flags behavior on compound pages: a worry Andrew Morton <akpm@linux-foundation.org> - 2015-08-12 23:20 +0200
          Re: page-flags behavior on compound pages: a worry "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-08-13 00:30 +0200
            Re: page-flags behavior on compound pages: a worry Hugh Dickins <hughd@google.com> - 2015-08-13 06:20 +0200

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