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SubjectRe: [PATCH -mm 06/21] mm, THP, swap: Support PMD swap mapping when splitting huge PMD
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On 04/16/18 19:02, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> A huge PMD need to be split when zap a part of the PMD mapping etc.
> If the PMD mapping is a swap mapping, we need to split it too. This
> patch implemented the support for this. This is similar as splitting
> the PMD page mapping, except we need to decrease the PMD swap mapping
> count for the huge swap cluster too. If the PMD swap mapping count
> becomes 0, the huge swap cluster will be split.
>
> Notice: is_huge_zero_pmd() and pmd_page() doesn't work well with swap
> PMD, so pmd_present() check is called before them.

FWIW, I would prefer to see that comment in the source code, not just
in the commit description.

>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Zi Yan <zi.yan@cs.rutgers.edu>
> ---
> include/linux/swap.h | 6 +++++
> mm/huge_memory.c | 54 ++++++++++++++++++++++++++++++++++++++++----
> mm/swapfile.c | 28 +++++++++++++++++++++++
> 3 files changed, 83 insertions(+), 5 deletions(-)


--
~Randy

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