[PATCHv8 25/32] shmem, thp: respect MADV_{NO,}HUGEPAGE for file mappings

Kirill A. Shutemov
2016-05-12T15:42:01Z

Let's wire up existing madvise() hugepage hints for file mappings.

MADV_HUGEPAGE advise shmem to allocate huge page on page fault in the
VMA. It only has effect if the filesystem is mounted with huge=advise or
huge=within_size.

MADV_NOHUGEPAGE prevents hugepage from being allocated on page fault in
the VMA. It doesn't prevent a huge page from being allocated by other
means, i.e. page fault into different mapping or write(2) into file.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/huge_memory.c | 19 +++++--------------
mm/shmem.c | 20 +++++++++++++++++---
2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 648f60d55759..3658b7d2c424 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1837,7 +1837,7 @@ spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
return NULL;
}

-#define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
+#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)

int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
@@ -1853,11 +1853,6 @@ int hugepage_madvise(struct vm_area_struct *vma,
if (mm_has_pgste(vma->vm_mm))
return 0;
#endif
- /*
- * Be somewhat over-protective like KSM for now!
- */
- if (*vm_flags & VM_NO_THP)
- return -EINVAL;
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
/*
@@ -1865,15 +1860,11 @@ int hugepage_madvise(struct vm_area_struct *vma,
* register it here without waiting a page fault that
* may not happen any time soon.
*/
- if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
+ if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
+ khugepaged_enter_vma_merge(vma, *vm_flags))
return -ENOMEM;
break;
case MADV_NOHUGEPAGE:
- /*
- * Be somewhat over-protective like KSM for now!
- */
- if (*vm_flags & VM_NO_THP)
- return -EINVAL;
*vm_flags &= ~VM_HUGEPAGE;
*vm_flags |= VM_NOHUGEPAGE;
/*
@@ -1984,7 +1975,7 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
if (vma->vm_ops)
/* khugepaged not yet working on file or special mappings */
return 0;
- VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
+ VM_BUG_ON_VMA(vm_flags & VM_NO_KHUGEPAGED, vma);
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
@@ -2373,7 +2364,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
return false;
if (is_vma_temporary_stack(vma))
return false;
- VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
+ VM_BUG_ON_VMA(vma->vm_flags & VM_NO_KHUGEPAGED, vma);
return true;
}

diff --git a/mm/shmem.c b/mm/shmem.c
index ec899b5ea9e6..872d658d37c0 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -101,6 +101,8 @@ struct shmem_falloc {
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 */
};
@@ -1409,6 +1411,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
struct mem_cgroup *memcg;
struct page *page;
swp_entry_t swap;
+ enum sgp_type sgp_huge = sgp;
pgoff_t hindex = index;
int error;
int once = 0;
@@ -1416,6 +1419,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,

if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
return -EFBIG;
+ if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
+ sgp = SGP_CACHE;
repeat:
swap.val = 0;
page = find_lock_entry(mapping, index);
@@ -1534,7 +1539,7 @@ repeat:
/* shmem_symlink() */
if (mapping->a_ops != &shmem_aops)
goto alloc_nohuge;
- if (shmem_huge == SHMEM_HUGE_DENY)
+ if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
goto alloc_nohuge;
if (shmem_huge == SHMEM_HUGE_FORCE)
goto alloc_huge;
@@ -1551,7 +1556,9 @@ repeat:
goto alloc_huge;
/* fallthrough */
case SHMEM_HUGE_ADVISE:
- /* TODO: wire up fadvise()/madvise() */
+ if (sgp_huge == SGP_HUGE)
+ goto alloc_huge;
+ /* TODO: implement fadvise() hints */
goto alloc_nohuge;
}

@@ -1680,6 +1687,7 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct inode *inode = file_inode(vma->vm_file);
gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
+ enum sgp_type sgp;
int error;
int ret = VM_FAULT_LOCKED;

@@ -1741,7 +1749,13 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
spin_unlock(&inode->i_lock);
}

- error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, SGP_CACHE,
+ sgp = SGP_CACHE;
+ if (vma->vm_flags & VM_HUGEPAGE)
+ sgp = SGP_HUGE;
+ else if (vma->vm_flags & VM_NOHUGEPAGE)
+ sgp = SGP_NOHUGE;
+
+ error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
gfp, vma->vm_mm, &ret);
if (error)
return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
--
2.8.1