On Wed, Sep 07, 2016 at 09:46:00AM -0700, Huang, Ying wrote: > From: Huang Ying <ying.hu...@intel.com> > > In this patch, the size of the swap cluster is changed to that of the > THP (Transparent Huge Page) on x86_64 architecture (512). This is for > the THP swap support on x86_64. Where one swap cluster will be used to > hold the contents of each THP swapped out. And some information of the > swapped out THP (such as compound map count) will be recorded in the > swap_cluster_info data structure. > > For other architectures which want THP swap support, THP_SWAP_CLUSTER > need to be selected in the Kconfig file for the architecture. > > In effect, this will enlarge swap cluster size by 2 times on x86_64. > Which may make it harder to find a free cluster when the swap space > becomes fragmented. So that, this may reduce the continuous swap space > allocation and sequential write in theory. The performance test in 0day > shows no regressions caused by this. > > Cc: Hugh Dickins <hu...@google.com> > Cc: Shaohua Li <s...@kernel.org> > Cc: Minchan Kim <minc...@kernel.org> > Cc: Rik van Riel <r...@redhat.com> > Suggested-by: Andrew Morton <a...@linux-foundation.org> > Signed-off-by: "Huang, Ying" <ying.hu...@intel.com> > --- > arch/x86/Kconfig | 1 + > mm/Kconfig | 13 +++++++++++++ > mm/swapfile.c | 4 ++++ > 3 files changed, 18 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 4c39728..421d862 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -164,6 +164,7 @@ config X86 > select HAVE_STACK_VALIDATION if X86_64 > select ARCH_USES_HIGH_VMA_FLAGS if > X86_INTEL_MEMORY_PROTECTION_KEYS > select ARCH_HAS_PKEYS if > X86_INTEL_MEMORY_PROTECTION_KEYS > + select ARCH_USES_THP_SWAP_CLUSTER if X86_64 > > config INSTRUCTION_DECODER > def_bool y > diff --git a/mm/Kconfig b/mm/Kconfig > index be0ee11..2da8128 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -503,6 +503,19 @@ config FRONTSWAP > > If unsure, say Y to enable frontswap. > > +config ARCH_USES_THP_SWAP_CLUSTER > + bool > + default n > + > +config THP_SWAP_CLUSTER > + bool > + depends on SWAP && TRANSPARENT_HUGEPAGE && ARCH_USES_THP_SWAP_CLUSTER > + default y > + help > + Use one swap cluster to hold the contents of the THP > + (Transparent Huge Page) swapped out. The size of the swap > + cluster will be same as that of THP. > +
Why do we need to ask user about it? I don't think most users qualified to make this decision. > config CMA > bool "Contiguous Memory Allocator" > depends on HAVE_MEMBLOCK && MMU > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 8f1b97d..4b78402 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -196,7 +196,11 @@ static void discard_swap_cluster(struct swap_info_struct > *si, > } > } > > +#ifdef CONFIG_THP_SWAP_CLUSTER Just #if defined(CONFIG_ARCH_USES_THP_SWAP_CLUSTER) && defined(CONFIG_TRANSPARENT_HUGEPAGE) would be enough from my POV. > +#define SWAPFILE_CLUSTER (HPAGE_SIZE / PAGE_SIZE) > +#else > #define SWAPFILE_CLUSTER 256 > +#endif > #define LATENCY_LIMIT 256 > > static inline void cluster_set_flag(struct swap_cluster_info *info, > -- > 2.8.1 > -- Kirill A. Shutemov
