[PATCH -mm 11/21] mm, THP, swap: Add sysfs interface to configure THP swapin

[Huang, Ying]

From: Huang Ying 

Swapin a THP as a whole isn't desirable at some situations.  For
example, for random access pattern, swapin a THP as a whole will
inflate the reading greatly.  So a sysfs interface:
/sys/kernel/mm/transparent_hugepage/swapin_enabled is added to
configure it.  Three options as follow are provided,

- always: THP swapin will be enabled always

- madvise: THP swapin will be enabled only for VMA with VM_HUGEPAGE
  flag set.

- never: THP swapin will be disabled always

The default configuration is: madvise.

During page fault, if a PMD swap mapping is found and THP swapin is
disabled, the huge swap cluster and the PMD swap mapping will be split
and fallback to normal page swapin.

Signed-off-by: "Huang, Ying" 
Cc: "Kirill A. Shutemov" 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Shaohua Li 
Cc: Hugh Dickins 
Cc: Minchan Kim 
Cc: Rik van Riel 
Cc: Dave Hansen 
Cc: Naoya Horiguchi 
Cc: Zi Yan 
---
 include/linux/huge_mm.h | 31 ++
 mm/huge_memory.c| 89 -
 2 files changed, 102 insertions(+), 18 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f5348d072351..1cfd43047f0d 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -62,6 +62,8 @@ enum transparent_hugepage_flag {
 #ifdef CONFIG_DEBUG_VM
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG,
 #endif
+   TRANSPARENT_HUGEPAGE_SWAPIN_FLAG,
+   TRANSPARENT_HUGEPAGE_SWAPIN_REQ_MADV_FLAG,
 };
 
 struct kobject;
@@ -404,11 +406,40 @@ static inline gfp_t alloc_hugepage_direct_gfpmask(struct 
vm_area_struct *vma)
 
 #ifdef CONFIG_THP_SWAP
 extern int do_huge_pmd_swap_page(struct vm_fault *vmf, pmd_t orig_pmd);
+
+static inline bool transparent_hugepage_swapin_enabled(
+   struct vm_area_struct *vma)
+{
+   if (vma->vm_flags & VM_NOHUGEPAGE)
+   return false;
+
+   if (is_vma_temporary_stack(vma))
+   return false;
+
+   if (test_bit(MMF_DISABLE_THP, >vm_mm->flags))
+   return false;
+
+   if (transparent_hugepage_flags &
+   (1 << TRANSPARENT_HUGEPAGE_SWAPIN_FLAG))
+   return true;
+
+   if (transparent_hugepage_flags &
+   (1 << TRANSPARENT_HUGEPAGE_SWAPIN_REQ_MADV_FLAG))
+   return !!(vma->vm_flags & VM_HUGEPAGE);
+
+   return false;
+}
 #else /* CONFIG_THP_SWAP */
 static inline int do_huge_pmd_swap_page(struct vm_fault *vmf, pmd_t orig_pmd)
 {
return 0;
 }
+
+static inline bool transparent_hugepage_swapin_enabled(
+   struct vm_area_struct *vma)
+{
+   return false;
+}
 #endif /* CONFIG_THP_SWAP */
 
 #endif /* _LINUX_HUGE_MM_H */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e4d32384e10b..0538fe48918b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -57,7 +57,8 @@ unsigned long transparent_hugepage_flags __read_mostly =
 #endif
(1<

[PATCH -mm 11/21] mm, THP, swap: Add sysfs interface to configure THP swapin

[Huang, Ying]

From: Huang Ying 

Swapin a THP as a whole isn't desirable at some situations.  For
example, for random access pattern, swapin a THP as a whole will
inflate the reading greatly.  So a sysfs interface:
/sys/kernel/mm/transparent_hugepage/swapin_enabled is added to
configure it.  Three options as follow are provided,

- always: THP swapin will be enabled always

- madvise: THP swapin will be enabled only for VMA with VM_HUGEPAGE
  flag set.

- never: THP swapin will be disabled always

The default configuration is: madvise.

During page fault, if a PMD swap mapping is found and THP swapin is
disabled, the huge swap cluster and the PMD swap mapping will be split
and fallback to normal page swapin.

Signed-off-by: "Huang, Ying" 
Cc: "Kirill A. Shutemov" 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Shaohua Li 
Cc: Hugh Dickins 
Cc: Minchan Kim 
Cc: Rik van Riel 
Cc: Dave Hansen 
Cc: Naoya Horiguchi 
Cc: Zi Yan 
---
 include/linux/huge_mm.h | 31 ++
 mm/huge_memory.c| 89 -
 2 files changed, 102 insertions(+), 18 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f5348d072351..1cfd43047f0d 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -62,6 +62,8 @@ enum transparent_hugepage_flag {
 #ifdef CONFIG_DEBUG_VM
TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG,
 #endif
+   TRANSPARENT_HUGEPAGE_SWAPIN_FLAG,
+   TRANSPARENT_HUGEPAGE_SWAPIN_REQ_MADV_FLAG,
 };
 
 struct kobject;
@@ -404,11 +406,40 @@ static inline gfp_t alloc_hugepage_direct_gfpmask(struct 
vm_area_struct *vma)
 
 #ifdef CONFIG_THP_SWAP
 extern int do_huge_pmd_swap_page(struct vm_fault *vmf, pmd_t orig_pmd);
+
+static inline bool transparent_hugepage_swapin_enabled(
+   struct vm_area_struct *vma)
+{
+   if (vma->vm_flags & VM_NOHUGEPAGE)
+   return false;
+
+   if (is_vma_temporary_stack(vma))
+   return false;
+
+   if (test_bit(MMF_DISABLE_THP, >vm_mm->flags))
+   return false;
+
+   if (transparent_hugepage_flags &
+   (1 << TRANSPARENT_HUGEPAGE_SWAPIN_FLAG))
+   return true;
+
+   if (transparent_hugepage_flags &
+   (1 << TRANSPARENT_HUGEPAGE_SWAPIN_REQ_MADV_FLAG))
+   return !!(vma->vm_flags & VM_HUGEPAGE);
+
+   return false;
+}
 #else /* CONFIG_THP_SWAP */
 static inline int do_huge_pmd_swap_page(struct vm_fault *vmf, pmd_t orig_pmd)
 {
return 0;
 }
+
+static inline bool transparent_hugepage_swapin_enabled(
+   struct vm_area_struct *vma)
+{
+   return false;
+}
 #endif /* CONFIG_THP_SWAP */
 
 #endif /* _LINUX_HUGE_MM_H */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e4d32384e10b..0538fe48918b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -57,7 +57,8 @@ unsigned long transparent_hugepage_flags __read_mostly =
 #endif
(1pmd, orig_pmd))) {
-   ret = split_swap_cluster(entry, false);
-   /*
-* Retry if somebody else swap in the swap
-* entry
-*/
-   if (ret == -EEXIST) {
-   ret = 0;
-   goto retry;
-   /* swapoff occurs under us */
-   } else if (ret == -EINVAL)
-   ret = 0;
-   else {
-   count_vm_event(THP_SWPIN_FALLBACK);
-   goto fallback;
-   }
-   }
+   if (likely(pmd_same(*vmf->pmd, orig_pmd)))
+   goto split;
delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
goto out;
}
@@ -1784,6 +1823,20 @@ int do_huge_pmd_swap_page(struct vm_fault *vmf, pmd_t 
orig_pmd)
if (page)
put_page(page);
return ret;
+split:
+   ret = split_swap_cluster(entry, false);
+   /* Retry if somebody else swap in the swap entry */
+   if (ret == -EEXIST) {
+   ret = 0;
+   goto retry;
+   }
+   /* swapoff occurs under