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    SubjectRe: [PATCHv2, RFC 00/30] Transparent huge page cache
    Hi Kirill,
    On 03/18/2013 07:19 PM, Kirill A. Shutemov wrote:
    > Simon Jeons wrote:
    >> On 03/18/2013 12:03 PM, Simon Jeons wrote:
    >>> Hi Kirill,
    >>> On 03/15/2013 01:50 AM, Kirill A. Shutemov wrote:
    >>>> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    >>>>
    >>>> Here's the second version of the patchset.
    >>>>
    >>>> The intend of the work is get code ready to enable transparent huge page
    >>>> cache for the most simple fs -- ramfs.
    >>>>
    >>>> We have read()/write()/mmap() functionality now. Still plenty work
    >>>> ahead.
    >>> One offline question.
    >>>
    >>> Why set PG_mlocked to page_tail which be splited in function
    >>> __split_huge_page_refcount?
    > Not set, but copied from head page. Head page represents up-to-date sate
    > of compound page, we need to copy it to all tail pages on split.

    I always see up-to-date state, could you conclude to me which state can
    be treated as up-to-date? :-)

    >
    >> Also why can't find where _PAGE_SPLITTING and _PAGE_PSE flags are
    >> cleared in split_huge_page path?
    >
    > The pmd is invalidated and replaced with reference to page table at the end
    > of __split_huge_page_map.

    Since pmd is populated by page table and new flag why need
    invalidated(clear present flag) before it?

    >
    >> Another offline question:
    >> Why don't clear tail page PG_tail flag in function
    >> __split_huge_page_refcount?
    > We do:
    >
    > page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
    >

    Got it.


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