diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/Kconfig | 11 | ||||
| -rw-r--r-- | mm/Makefile | 1 | ||||
| -rw-r--r-- | mm/ksm.c | 56 | ||||
| -rw-r--r-- | mm/madvise.c | 14 |
4 files changed, 82 insertions, 0 deletions
@@ -214,6 +214,17 @@ config HAVE_MLOCKED_PAGE_BIT config MMU_NOTIFIER bool +config KSM + bool "Enable KSM for page merging" + depends on MMU + help + Enable Kernel Samepage Merging: KSM periodically scans those areas + of an application's address space that an app has advised may be + mergeable. When it finds pages of identical content, it replaces + the many instances by a single resident page with that content, so + saving memory until one or another app needs to modify the content. + Recommended for use with KVM, or with other duplicative applications. + config DEFAULT_MMAP_MIN_ADDR int "Low address space to protect from user allocation" default 4096 diff --git a/mm/Makefile b/mm/Makefile index ea4b18b..a63bf59 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -25,6 +25,7 @@ obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o obj-$(CONFIG_TMPFS_POSIX_ACL) += shmem_acl.o obj-$(CONFIG_SLOB) += slob.o obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o +obj-$(CONFIG_KSM) += ksm.o obj-$(CONFIG_PAGE_POISONING) += debug-pagealloc.o obj-$(CONFIG_SLAB) += slab.o obj-$(CONFIG_SLUB) += slub.o diff --git a/mm/ksm.c b/mm/ksm.c new file mode 100644 index 0000000..8b76008 --- /dev/null +++ b/mm/ksm.c @@ -0,0 +1,56 @@ +/* + * Initial dummy version just to illustrate KSM's interface to other files. + */ + +#include <linux/errno.h> +#include <linux/mman.h> +#include <linux/ksm.h> + +int ksm_madvise(struct vm_area_struct *vma, unsigned long start, + unsigned long end, int advice, unsigned long *vm_flags) +{ + struct mm_struct *mm = vma->vm_mm; + + switch (advice) { + case MADV_MERGEABLE: + /* + * Be somewhat over-protective for now! + */ + if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | + VM_PFNMAP | VM_IO | VM_DONTEXPAND | + VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | + VM_MIXEDMAP | VM_SAO)) + return 0; /* just ignore the advice */ + + if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) + if (__ksm_enter(mm) < 0) + return -EAGAIN; + + *vm_flags |= VM_MERGEABLE; + break; + + case MADV_UNMERGEABLE: + if (!(*vm_flags & VM_MERGEABLE)) + return 0; /* just ignore the advice */ + + /* Unmerge any merged pages here */ + + *vm_flags &= ~VM_MERGEABLE; + break; + } + + return 0; +} + +int __ksm_enter(struct mm_struct *mm) +{ + /* Allocate a structure to track mm and link it into KSM's list */ + set_bit(MMF_VM_MERGEABLE, &mm->flags); + return 0; +} + +void __ksm_exit(struct mm_struct *mm) +{ + /* Unlink and free all KSM's structures which track this mm */ + clear_bit(MMF_VM_MERGEABLE, &mm->flags); +} diff --git a/mm/madvise.c b/mm/madvise.c index 66c3126..d9ae206 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -11,6 +11,7 @@ #include <linux/mempolicy.h> #include <linux/hugetlb.h> #include <linux/sched.h> +#include <linux/ksm.h> /* * Any behaviour which results in changes to the vma->vm_flags needs to @@ -63,6 +64,12 @@ static long madvise_behavior(struct vm_area_struct * vma, } new_flags &= ~VM_DONTCOPY; break; + case MADV_MERGEABLE: + case MADV_UNMERGEABLE: + error = ksm_madvise(vma, start, end, behavior, &new_flags); + if (error) + goto out; + break; } if (new_flags == vma->vm_flags) { @@ -239,6 +246,10 @@ madvise_behavior_valid(int behavior) case MADV_REMOVE: case MADV_WILLNEED: case MADV_DONTNEED: +#ifdef CONFIG_KSM + case MADV_MERGEABLE: + case MADV_UNMERGEABLE: +#endif return 1; default: @@ -273,6 +284,9 @@ madvise_behavior_valid(int behavior) * MADV_DONTFORK - omit this area from child's address space when forking: * typically, to avoid COWing pages pinned by get_user_pages(). * MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking. + * MADV_MERGEABLE - the application recommends that KSM try to merge pages in + * this area with pages of identical content from other such areas. + * MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others. * * return values: * zero - success |
