On Mon, Jul 07, 2014 at 02:13:03PM +0300, Kirill A. Shutemov wrote:
On Mon, Jul 07, 2014 at 09:53:58AM +0900, Minchan Kim wrote:
quoted
We don't need to split THP page when MADV_FREE syscall is
called. It could be done when VM decide really frees it so
we could reduce the number of THP split.
Signed-off-by: Minchan Kim <redacted>
---
include/linux/huge_mm.h | 3 +++
mm/huge_memory.c | 25 +++++++++++++++++++++++++
mm/madvise.c | 19 +++++++++++++++++--
mm/rmap.c | 4 ++++
mm/vmscan.c | 24 ++++++++++++++++--------
5 files changed, 65 insertions(+), 10 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 63579cb8d3dc..f0d37238cf8f 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -19,6 +19,9 @@ extern struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags);
+extern int madvise_free_pmd(struct mmu_gather *tlb,
+ struct vm_area_struct *vma,
+ pmd_t *pmd, unsigned long addr);
extern int zap_huge_pmd(struct mmu_gather *tlb,
struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5d562a9fe931..2a70069dcfc0 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1384,6 +1384,31 @@ out:
return 0;
}
+int madvise_free_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ pmd_t *pmd, unsigned long addr)
+{
+ spinlock_t *ptl;
+ int ret = 0;
+
+ if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ pmd_t orig_pmd;
+ struct mm_struct *mm = vma->vm_mm;
+
+ /* No hugepage in swapcache */
+ VM_BUG_ON(PageSwapCache(pmd_page(orig_pmd)));
VM_BUG_ON_PAGE() ?
NP.
quoted
+
+ orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
+ orig_pmd = pmd_mkold(orig_pmd);
+ orig_pmd = pmd_mkclean(orig_pmd);
+
+ set_pmd_at(mm, addr, pmd, orig_pmd);
+ tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ spin_unlock(ptl);
+ ret = 1;
+ }
+ return ret;
+}
+
int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr)
{diff --git a/mm/madvise.c b/mm/madvise.c
index 372a25a8ea82..3c99919ee094 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -320,8 +320,23 @@ static inline unsigned long madvise_free_pmd_range(struct mmu_gather *tlb,
* if the range covers.
*/
next = pmd_addr_end(addr, end);
- if (pmd_trans_huge(*pmd))
- split_huge_page_pmd(vma, addr, pmd);
+ if (pmd_trans_huge(*pmd)) {
+ if (next - addr != HPAGE_PMD_SIZE) {
+#ifdef CONFIG_DEBUG_VM
+ if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
+ pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
+ __func__, addr, end,
+ vma->vm_start,
+ vma->vm_end);
+ BUG();
+ }
+#endif
+ split_huge_page_pmd(vma, addr, pmd);
+ } else if (madvise_free_pmd(tlb, vma, pmd, addr))
+ goto next;
+ /* fall through */
+ }
+
/*
* Here there can be other concurrent MADV_DONTNEED or
* trans huge page faults running, and if the pmd isdiff --git a/mm/rmap.c b/mm/rmap.c
index ee495d84c8b3..3c415eb8b6f0 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -702,6 +702,10 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
/* go ahead even if the pmd is pmd_trans_splitting() */
if (pmdp_clear_flush_young_notify(vma, address, pmd))
referenced++;
+
+ if (pmd_dirty(*pmd))
+ dirty++;
+
spin_unlock(ptl);
} else {
pte_t *pte;diff --git a/mm/vmscan.c b/mm/vmscan.c
index f7a45600846f..4e15babf4414 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -971,15 +971,23 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
- if (PageAnon(page) && !PageSwapCache(page) && !freeable) {
- if (!(sc->gfp_mask & __GFP_IO))
- goto keep_locked;
- if (!add_to_swap(page, page_list))
- goto activate_locked;
- may_enter_fs = 1;
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ if (!freeable) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (!add_to_swap(page, page_list))
+ goto activate_locked;
+ may_enter_fs = 1;
- /* Adding to swap updated mapping */
- mapping = page_mapping(page);
+ /* Adding to swap updated mapping */
+ mapping = page_mapping(page);
+ } else {
+ if (unlikely(PageTransHuge(page))) {
+ if (unlikely(split_huge_page_to_list(
+ page, page_list)))
+ goto keep_locked;
Hm. It would be better to free the huge page without splitting.
It shouldn't be a big deal: walk over rmap and zap all pmds.
Or I miss something?
Actually, I did but found no problem except CONFIG_DEBUG_VM but rollback
after peeking [1].
When I read the description in detail by your review, I think we can remove
BUG_ON(PageTransHuge(page)) in try_to_unmap and go with no split for lazyfree
page because they are not in swapcache any more so the assumption of [1] is
not valid. Will do it in next revision.
Thanks for the review, Kirill!
[1] thp: split_huge_page paging, 3f04f62f9
quoted
+ }
+ }
}
/*
--
2.0.0
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Kirill A. Shutemov
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Kind regards,
Minchan Kim