khugepaged: add support of collapse for tmpfs/shmem pages
This patch extends khugepaged to support collapse of tmpfs/shmem pages.
We share fair amount of infrastructure with anon-THP collapse.
Few design points:
- First we are looking for VMA which can be suitable for mapping huge
page;
- If the VMA maps shmem file, the rest scan/collapse operations
operates on page cache, not on page tables as in anon VMA case.
- khugepaged_scan_shmem() finds a range which is suitable for huge
page. The scan is lockless and shouldn't disturb system too much.
- once the candidate for collapse is found, collapse_shmem() attempts
to create a huge page:
+ scan over radix tree, making the range point to new huge page;
+ new huge page is not-uptodate, locked and freezed (refcount
is 0), so nobody can touch them until we say so.
+ we swap in pages during the scan. khugepaged_scan_shmem()
filters out ranges with more than khugepaged_max_ptes_swap
swapped out pages. It's HPAGE_PMD_NR/8 by default.
+ old pages are isolated, unmapped and put to local list in case
to be restored back if collapse failed.
- if collapse succeed, we retract pte page tables from VMAs where huge
pages mapping is possible. The huge page will be mapped as PMD on
next minor fault into the range.
Link: http://lkml.kernel.org/r/1466021202-61880-35-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index 03eb915..905c0e1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -32,6 +32,7 @@
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/uio.h>
+#include <linux/khugepaged.h>
static struct vfsmount *shm_mnt;
@@ -97,16 +98,6 @@
pgoff_t nr_unswapped; /* how often writepage refused to swap out */
};
-/* Flag allocation requirements to shmem_getpage */
-enum sgp_type {
- SGP_READ, /* don't exceed i_size, don't allocate page */
- SGP_CACHE, /* don't exceed i_size, may allocate page */
- SGP_NOHUGE, /* like SGP_CACHE, but no huge pages */
- SGP_HUGE, /* like SGP_CACHE, huge pages preferred */
- SGP_WRITE, /* may exceed i_size, may allocate !Uptodate page */
- SGP_FALLOC, /* like SGP_WRITE, but make existing page Uptodate */
-};
-
#ifdef CONFIG_TMPFS
static unsigned long shmem_default_max_blocks(void)
{
@@ -126,7 +117,7 @@
struct page **pagep, enum sgp_type sgp,
gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
-static inline int shmem_getpage(struct inode *inode, pgoff_t index,
+int shmem_getpage(struct inode *inode, pgoff_t index,
struct page **pagep, enum sgp_type sgp)
{
return shmem_getpage_gfp(inode, index, pagep, sgp,
@@ -1899,6 +1890,11 @@
{
file_accessed(file);
vma->vm_ops = &shmem_vm_ops;
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+ ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+ (vma->vm_end & HPAGE_PMD_MASK)) {
+ khugepaged_enter(vma, vma->vm_flags);
+ }
return 0;
}
@@ -3803,6 +3799,37 @@
struct kobj_attribute shmem_enabled_attr =
__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
+
+bool shmem_huge_enabled(struct vm_area_struct *vma)
+{
+ struct inode *inode = file_inode(vma->vm_file);
+ struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+ loff_t i_size;
+ pgoff_t off;
+
+ if (shmem_huge == SHMEM_HUGE_FORCE)
+ return true;
+ if (shmem_huge == SHMEM_HUGE_DENY)
+ return false;
+ switch (sbinfo->huge) {
+ case SHMEM_HUGE_NEVER:
+ return false;
+ case SHMEM_HUGE_ALWAYS:
+ return true;
+ case SHMEM_HUGE_WITHIN_SIZE:
+ off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
+ i_size = round_up(i_size_read(inode), PAGE_SIZE);
+ if (i_size >= HPAGE_PMD_SIZE &&
+ i_size >> PAGE_SHIFT >= off)
+ return true;
+ case SHMEM_HUGE_ADVISE:
+ /* TODO: implement fadvise() hints */
+ return (vma->vm_flags & VM_HUGEPAGE);
+ default:
+ VM_BUG_ON(1);
+ return false;
+ }
+}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
#else /* !CONFIG_SHMEM */
@@ -3982,6 +4009,13 @@
fput(vma->vm_file);
vma->vm_file = file;
vma->vm_ops = &shmem_vm_ops;
+
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+ ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+ (vma->vm_end & HPAGE_PMD_MASK)) {
+ khugepaged_enter(vma, vma->vm_flags);
+ }
+
return 0;
}
