"Kirill A. Shutemov" <kir...@shutemov.name> writes: > 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.
Users need not to choose this. If the dependencies is true, it will be turned on. I added the help here not for users, but for developers to know what it is for. >> 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. That works. I added a new configuration option just to save some typing and make it a little easier to read. If other people think it is not necessary to add a new configuration option for that too. I will use change it in this way. Best Regards, Huang, Ying >> +#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 >>
