The hugepage_vma_check() could be reused by khugepaged_enter() and
khugepaged_enter_vma_merge(), but it is static in khugepaged.c.
Make it non-static and declare it in khugepaged.h.
Suggested-by: Vlastimil Babka <[email protected]>
Signed-off-by: Yang Shi <[email protected]>
---
include/linux/khugepaged.h | 14 ++++++--------
mm/khugepaged.c | 25 +++++++++----------------
2 files changed, 15 insertions(+), 24 deletions(-)
diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index 0423d3619f26..c340f6bb39d6 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -3,8 +3,6 @@
#define _LINUX_KHUGEPAGED_H
#include <linux/sched/coredump.h> /* MMF_VM_HUGEPAGE */
-#include <linux/shmem_fs.h>
-
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern struct attribute_group khugepaged_attr_group;
@@ -12,6 +10,8 @@ extern struct attribute_group khugepaged_attr_group;
extern int khugepaged_init(void);
extern void khugepaged_destroy(void);
extern int start_stop_khugepaged(void);
+extern bool hugepage_vma_check(struct vm_area_struct *vma,
+ unsigned long vm_flags);
extern void __khugepaged_enter(struct mm_struct *mm);
extern void __khugepaged_exit(struct mm_struct *mm);
extern void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
@@ -55,13 +55,11 @@ static inline void khugepaged_exit(struct mm_struct *mm)
static inline void khugepaged_enter(struct vm_area_struct *vma,
unsigned long vm_flags)
{
- if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
- if ((khugepaged_always() ||
- (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) ||
- (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
- !(vm_flags & VM_NOHUGEPAGE) &&
- !test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
+ if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
+ khugepaged_enabled()) {
+ if (hugepage_vma_check(vma, vm_flags))
__khugepaged_enter(vma->vm_mm);
+ }
}
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 7815218ab960..dec449339964 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -437,8 +437,8 @@ static inline int khugepaged_test_exit(struct mm_struct *mm)
return atomic_read(&mm->mm_users) == 0;
}
-static bool hugepage_vma_check(struct vm_area_struct *vma,
- unsigned long vm_flags)
+bool hugepage_vma_check(struct vm_area_struct *vma,
+ unsigned long vm_flags)
{
if (!transhuge_vma_enabled(vma, vm_flags))
return false;
@@ -508,20 +508,13 @@ void __khugepaged_enter(struct mm_struct *mm)
void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
- unsigned long hstart, hend;
-
- /*
- * khugepaged only supports read-only files for non-shmem files.
- * khugepaged does not yet work on special mappings. And
- * file-private shmem THP is not supported.
- */
- if (!hugepage_vma_check(vma, vm_flags))
- return;
-
- hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
- hend = vma->vm_end & HPAGE_PMD_MASK;
- if (hstart < hend)
- khugepaged_enter(vma, vm_flags);
+ if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
+ khugepaged_enabled() &&
+ (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
+ (vma->vm_end & HPAGE_PMD_MASK))) {
+ if (hugepage_vma_check(vma, vm_flags))
+ __khugepaged_enter(vma->vm_mm);
+ }
}
void __khugepaged_exit(struct mm_struct *mm)
--
2.26.3
On Tue, 10 May 2022 13:32:20 -0700 Yang Shi <[email protected]> wrote:
> The hugepage_vma_check() could be reused by khugepaged_enter() and
> khugepaged_enter_vma_merge(), but it is static in khugepaged.c.
> Make it non-static and declare it in khugepaged.h.
>
> ..
>
> @@ -508,20 +508,13 @@ void __khugepaged_enter(struct mm_struct *mm)
> void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> - unsigned long hstart, hend;
> -
> - /*
> - * khugepaged only supports read-only files for non-shmem files.
> - * khugepaged does not yet work on special mappings. And
> - * file-private shmem THP is not supported.
> - */
> - if (!hugepage_vma_check(vma, vm_flags))
> - return;
> -
> - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
> - hend = vma->vm_end & HPAGE_PMD_MASK;
> - if (hstart < hend)
> - khugepaged_enter(vma, vm_flags);
> + if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> + khugepaged_enabled() &&
> + (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
> + (vma->vm_end & HPAGE_PMD_MASK))) {
Reviewing these bounds-checking tests is so hard :( Can we simplify?
> + if (hugepage_vma_check(vma, vm_flags))
> + __khugepaged_enter(vma->vm_mm);
> + }
> }
void khugepaged_enter_vma(struct vm_area_struct *vma,
unsigned long vm_flags)
{
if (test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
return;
if (!khugepaged_enabled())
return;
if (round_up(vma->vm_start, HPAGE_PMD_SIZE) >=
(vma->vm_end & HPAGE_PMD_MASK))
return; /* vma is too small */
if (!hugepage_vma_check(vma, vm_flags))
return;
__khugepaged_enter(vma->vm_mm);
}
Also, it might be slightly faster to have checked MMF_VM_HUGEPAGE
before khugepaged_enabled(), but it looks odd. And it might be slower,
too - more pointer chasing.
I wish someone would document hugepage_vma_check().
On Tue, May 10, 2022 at 2:05 PM Andrew Morton <[email protected]> wrote:
>
> On Tue, 10 May 2022 13:32:20 -0700 Yang Shi <[email protected]> wrote:
>
> > The hugepage_vma_check() could be reused by khugepaged_enter() and
> > khugepaged_enter_vma_merge(), but it is static in khugepaged.c.
> > Make it non-static and declare it in khugepaged.h.
> >
> > ..
> >
> > @@ -508,20 +508,13 @@ void __khugepaged_enter(struct mm_struct *mm)
> > void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
> > unsigned long vm_flags)
> > {
> > - unsigned long hstart, hend;
> > -
> > - /*
> > - * khugepaged only supports read-only files for non-shmem files.
> > - * khugepaged does not yet work on special mappings. And
> > - * file-private shmem THP is not supported.
> > - */
> > - if (!hugepage_vma_check(vma, vm_flags))
> > - return;
> > -
> > - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
> > - hend = vma->vm_end & HPAGE_PMD_MASK;
> > - if (hstart < hend)
> > - khugepaged_enter(vma, vm_flags);
> > + if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> > + khugepaged_enabled() &&
> > + (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
> > + (vma->vm_end & HPAGE_PMD_MASK))) {
>
> Reviewing these bounds-checking tests is so hard :( Can we simplify?
Yeah, I think they can be moved into a helper with a more descriptive name.
>
> > + if (hugepage_vma_check(vma, vm_flags))
> > + __khugepaged_enter(vma->vm_mm);
> > + }
> > }
>
> void khugepaged_enter_vma(struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> if (test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
> return;
> if (!khugepaged_enabled())
> return;
> if (round_up(vma->vm_start, HPAGE_PMD_SIZE) >=
> (vma->vm_end & HPAGE_PMD_MASK))
> return; /* vma is too small */
> if (!hugepage_vma_check(vma, vm_flags))
> return;
> __khugepaged_enter(vma->vm_mm);
> }
>
>
> Also, it might be slightly faster to have checked MMF_VM_HUGEPAGE
> before khugepaged_enabled(), but it looks odd. And it might be slower,
> too - more pointer chasing.
I think most configurations have always or madvise mode set
(khugepaged_enabled() return true), so having checked MMF_VM_HUGEPAGE
before khugepaged_enabled() seems slightly better, but anyway it
should not have measurable effect IMHO.
>
> I wish someone would document hugepage_vma_check().
I will clean up all the stuff further in a new patchset, for example,
trying to consolidate all the different
hugepage_suitable/enabled/active checks.