On Sun, Jul 8, 2018 at 10:40 PM, Huang, Ying <ying.huang@xxxxxxxxx> wrote: > Dan Williams <dan.j.williams@xxxxxxxxx> writes: > >> On Thu, Jun 21, 2018 at 8:55 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: >>> >>> From: Huang Ying <ying.huang@xxxxxxxxx> >>> >>> Previously, the PMD swap operations are only enabled for >>> CONFIG_ARCH_ENABLE_THP_MIGRATION. Because they are only used by the >>> THP migration support. We will support PMD swap mapping to the huge >>> swap cluster and swapin the THP as a whole. That will be enabled via >>> CONFIG_THP_SWAP and needs these PMD swap operations. So enable the >>> PMD swap operations for CONFIG_THP_SWAP 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> >>> Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> >>> --- >>> arch/x86/include/asm/pgtable.h | 2 +- >>> include/asm-generic/pgtable.h | 2 +- >>> include/linux/swapops.h | 44 ++++++++++++++++++++++-------------------- >>> 3 files changed, 25 insertions(+), 23 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >>> index 99ecde23c3ec..13bf58838daf 100644 >>> --- a/arch/x86/include/asm/pgtable.h >>> +++ b/arch/x86/include/asm/pgtable.h >>> @@ -1224,7 +1224,7 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) >>> return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY); >>> } >>> >>> -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION >>> +#if defined(CONFIG_ARCH_ENABLE_THP_MIGRATION) || defined(CONFIG_THP_SWAP) >> >> How about introducing a new config symbol representing the common >> infrastructure between the two and have them select that symbol. > > The common infrastructure shared by two mechanisms is PMD swap entry. > But I didn't find there are many places where the common infrastructure > is used. So I think it may be over-engineering to introduce a new > config symbol but use it for so few times. > >> Would that also allow us to clean up the usage of >> CONFIG_ARCH_ENABLE_THP_MIGRATION in fs/proc/task_mmu.c? In other >> words, what's the point of having nice ifdef'd alternatives in header >> files when ifdefs are still showing up in C files, all of it should be >> optionally determined by header files. > > Unfortunately, I think it is not a easy task to wrap all C code via > #ifdef in header files. And it may be over-engineering to wrap them > all. I guess this is why there are still some #ifdef in C files. That's the entire point. Yes, over-engineer the header files so the actual C code is more readable.
