Re: [PATCH -mm 06/21] mm, THP, swap: Support PMD swap mapping when splitting huge PMD
From: Huang\, Ying
Date: Tue Apr 17 2018 - 20:38:26 EST
Randy Dunlap <rdunlap@xxxxxxxxxxxxx> writes:
> On 04/16/18 19:02, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@xxxxxxxxx>
>> 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.
Sure. I will add comment in source code too.
>> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
>> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Cc: Shaohua Li <shli@xxxxxxxxxx>
>> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
>> Cc: Minchan Kim <minchan@xxxxxxxxxx>
>> Cc: Rik van Riel <riel@xxxxxxxxxx>
>> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
>> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
>> include/linux/swap.h | 6 +++++
>> mm/huge_memory.c | 54 ++++++++++++++++++++++++++++++++++++++++----
>> mm/swapfile.c | 28 +++++++++++++++++++++++
>> 3 files changed, 83 insertions(+), 5 deletions(-)