[PATCH 1/2] hugetlbfs: support split page table lock
From: Naoya Horiguchi
Date: Tue May 28 2013 - 15:54:07 EST
Currently all of page table handling by hugetlbfs code are done under
mm->page_table_lock. This is not optimal because there can be lock
contentions between unrelated components using this lock.
This patch makes hugepage support split page table lock so that
we use page->ptl of the leaf node of page table tree which is pte for
normal pages but can be pmd and/or pud for hugepages of some architectures.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
arch/x86/mm/hugetlbpage.c | 6 ++--
include/linux/hugetlb.h | 18 ++++++++++
mm/hugetlb.c | 84 ++++++++++++++++++++++++++++-------------------
3 files changed, 73 insertions(+), 35 deletions(-)
diff --git v3.10-rc3.orig/arch/x86/mm/hugetlbpage.c v3.10-rc3/arch/x86/mm/hugetlbpage.c
index ae1aa71..0e4a396 100644
--- v3.10-rc3.orig/arch/x86/mm/hugetlbpage.c
+++ v3.10-rc3/arch/x86/mm/hugetlbpage.c
@@ -75,6 +75,7 @@ huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
unsigned long saddr;
pte_t *spte = NULL;
pte_t *pte;
+ spinlock_t *ptl;
if (!vma_shareable(vma, addr))
return (pte_t *)pmd_alloc(mm, pud, addr);
@@ -89,6 +90,7 @@ huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
spte = huge_pte_offset(svma->vm_mm, saddr);
if (spte) {
get_page(virt_to_page(spte));
+ ptl = huge_pte_lockptr(mm, spte);
break;
}
}
@@ -97,12 +99,12 @@ huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
if (!spte)
goto out;
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
if (pud_none(*pud))
pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
else
put_page(virt_to_page(spte));
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
out:
pte = (pte_t *)pmd_alloc(mm, pud, addr);
mutex_unlock(&mapping->i_mmap_mutex);
diff --git v3.10-rc3.orig/include/linux/hugetlb.h v3.10-rc3/include/linux/hugetlb.h
index a639c87..40f3215 100644
--- v3.10-rc3.orig/include/linux/hugetlb.h
+++ v3.10-rc3/include/linux/hugetlb.h
@@ -32,6 +32,24 @@ void hugepage_put_subpool(struct hugepage_subpool *spool);
int PageHuge(struct page *page);
+#if USE_SPLIT_PTLOCKS
+#define huge_pte_lockptr(mm, ptep) ({__pte_lockptr(virt_to_page(ptep)); })
+#else /* !USE_SPLIT_PTLOCKS */
+#define huge_pte_lockptr(mm, ptep) ({&(mm)->page_table_lock; })
+#endif /* USE_SPLIT_PTLOCKS */
+
+#define huge_pte_offset_lock(mm, address, ptlp) \
+({ \
+ pte_t *__pte = huge_pte_offset(mm, address); \
+ spinlock_t *__ptl = NULL; \
+ if (__pte) { \
+ __ptl = huge_pte_lockptr(mm, __pte); \
+ *(ptlp) = __ptl; \
+ spin_lock(__ptl); \
+ } \
+ __pte; \
+})
+
void reset_vma_resv_huge_pages(struct vm_area_struct *vma);
int hugetlb_sysctl_handler(struct ctl_table *, int, void __user *, size_t *, loff_t *);
int hugetlb_overcommit_handler(struct ctl_table *, int, void __user *, size_t *, loff_t *);
diff --git v3.10-rc3.orig/mm/hugetlb.c v3.10-rc3/mm/hugetlb.c
index 463fb5e..8e1af32 100644
--- v3.10-rc3.orig/mm/hugetlb.c
+++ v3.10-rc3/mm/hugetlb.c
@@ -2325,6 +2325,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) {
+ spinlock_t *srcptl, *dstptl;
src_pte = huge_pte_offset(src, addr);
if (!src_pte)
continue;
@@ -2336,8 +2337,10 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
if (dst_pte == src_pte)
continue;
- spin_lock(&dst->page_table_lock);
- spin_lock_nested(&src->page_table_lock, SINGLE_DEPTH_NESTING);
+ dstptl = huge_pte_lockptr(dst, dst_pte);
+ srcptl = huge_pte_lockptr(src, src_pte);
+ spin_lock(dstptl);
+ spin_lock_nested(srcptl, SINGLE_DEPTH_NESTING);
if (!huge_pte_none(huge_ptep_get(src_pte))) {
if (cow)
huge_ptep_set_wrprotect(src, addr, src_pte);
@@ -2347,8 +2350,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
page_dup_rmap(ptepage);
set_huge_pte_at(dst, addr, dst_pte, entry);
}
- spin_unlock(&src->page_table_lock);
- spin_unlock(&dst->page_table_lock);
+ spin_unlock(srcptl);
+ spin_unlock(dstptl);
}
return 0;
@@ -2391,6 +2394,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
unsigned long address;
pte_t *ptep;
pte_t pte;
+ spinlock_t *ptl;
struct page *page;
struct hstate *h = hstate_vma(vma);
unsigned long sz = huge_page_size(h);
@@ -2404,25 +2408,24 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
tlb_start_vma(tlb, vma);
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
again:
- spin_lock(&mm->page_table_lock);
for (address = start; address < end; address += sz) {
- ptep = huge_pte_offset(mm, address);
+ ptep = huge_pte_offset_lock(mm, address, &ptl);
if (!ptep)
continue;
if (huge_pmd_unshare(mm, &address, ptep))
- continue;
+ goto unlock;
pte = huge_ptep_get(ptep);
if (huge_pte_none(pte))
- continue;
+ goto unlock;
/*
* HWPoisoned hugepage is already unmapped and dropped reference
*/
if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
huge_pte_clear(mm, address, ptep);
- continue;
+ goto unlock;
}
page = pte_page(pte);
@@ -2433,7 +2436,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
*/
if (ref_page) {
if (page != ref_page)
- continue;
+ goto unlock;
/*
* Mark the VMA as having unmapped its page so that
@@ -2450,13 +2453,18 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
page_remove_rmap(page);
force_flush = !__tlb_remove_page(tlb, page);
- if (force_flush)
+ if (force_flush) {
+ spin_unlock(ptl);
break;
+ }
/* Bail out after unmapping reference page if supplied */
- if (ref_page)
+ if (ref_page) {
+ spin_unlock(ptl);
break;
+ }
+unlock:
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
/*
* mmu_gather ran out of room to batch pages, we break out of
* the PTE lock to avoid doing the potential expensive TLB invalidate
@@ -2570,6 +2578,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
int outside_reserve = 0;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
+ spinlock_t *ptl = huge_pte_lockptr(mm, ptep);
old_page = pte_page(pte);
@@ -2601,7 +2610,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
page_cache_get(old_page);
/* Drop page_table_lock as buddy allocator may be called */
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
new_page = alloc_huge_page(vma, address, outside_reserve);
if (IS_ERR(new_page)) {
@@ -2619,7 +2628,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
BUG_ON(huge_pte_none(pte));
if (unmap_ref_private(mm, vma, old_page, address)) {
BUG_ON(huge_pte_none(pte));
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte)))
goto retry_avoidcopy;
@@ -2633,7 +2642,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
}
/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
if (err == -ENOMEM)
return VM_FAULT_OOM;
else
@@ -2648,7 +2657,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
page_cache_release(new_page);
page_cache_release(old_page);
/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
return VM_FAULT_OOM;
}
@@ -2663,7 +2672,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
* Retake the page_table_lock to check for racing updates
* before the page tables are altered
*/
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
ptep = huge_pte_offset(mm, address & huge_page_mask(h));
if (likely(pte_same(huge_ptep_get(ptep), pte))) {
/* Break COW */
@@ -2675,10 +2684,10 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
/* Make the old page be freed below */
new_page = old_page;
}
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
/* Caller expects lock to be held */
- spin_lock(&mm->page_table_lock);
+ spin_lock(ptl);
page_cache_release(new_page);
page_cache_release(old_page);
return 0;
@@ -2728,6 +2737,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page *page;
struct address_space *mapping;
pte_t new_pte;
+ spinlock_t *ptl;
/*
* Currently, we are forced to kill the process in the event the
@@ -2813,7 +2823,8 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
goto backout_unlocked;
}
- spin_lock(&mm->page_table_lock);
+ ptl = huge_pte_lockptr(mm, ptep);
+ spin_lock(ptl);
size = i_size_read(mapping->host) >> huge_page_shift(h);
if (idx >= size)
goto backout;
@@ -2835,13 +2846,13 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
ret = hugetlb_cow(mm, vma, address, ptep, new_pte, page);
}
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
unlock_page(page);
out:
return ret;
backout:
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
backout_unlocked:
unlock_page(page);
put_page(page);
@@ -2853,6 +2864,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
{
pte_t *ptep;
pte_t entry;
+ spinlock_t *ptl;
int ret;
struct page *page = NULL;
struct page *pagecache_page = NULL;
@@ -2921,7 +2933,8 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (page != pagecache_page)
lock_page(page);
- spin_lock(&mm->page_table_lock);
+ ptl = huge_pte_lockptr(mm, ptep);
+ spin_lock(ptl);
/* Check for a racing update before calling hugetlb_cow */
if (unlikely(!pte_same(entry, huge_ptep_get(ptep))))
goto out_page_table_lock;
@@ -2941,7 +2954,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
update_mmu_cache(vma, address, ptep);
out_page_table_lock:
- spin_unlock(&mm->page_table_lock);
+ spin_unlock(ptl);
if (pagecache_page) {
unlock_page(pagecache_page);
@@ -2976,9 +2989,9 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long remainder = *nr_pages;
struct hstate *h = hstate_vma(vma);
- spin_lock(&mm->page_table_lock);
while (vaddr < vma->vm_end && remainder) {
pte_t *pte;
+ spinlock_t *ptl = NULL;
int absent;
struct page *page;
@@ -2986,8 +2999,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
* first, for the page indexing below to work.
+ *
+ * Note that page table lock is not held when pte is null.
*/
- pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
+ pte = huge_pte_offset_lock(mm, vaddr & huge_page_mask(h), &ptl);
absent = !pte || huge_pte_none(huge_ptep_get(pte));
/*
@@ -2999,6 +3014,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
if (absent && (flags & FOLL_DUMP) &&
!hugetlbfs_pagecache_present(h, vma, vaddr)) {
+ if (pte)
+ spin_unlock(ptl);
remainder = 0;
break;
}
@@ -3018,10 +3035,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
!huge_pte_write(huge_ptep_get(pte)))) {
int ret;
- spin_unlock(&mm->page_table_lock);
+ if (pte)
+ spin_unlock(ptl);
ret = hugetlb_fault(mm, vma, vaddr,
(flags & FOLL_WRITE) ? FAULT_FLAG_WRITE : 0);
- spin_lock(&mm->page_table_lock);
if (!(ret & VM_FAULT_ERROR))
continue;
@@ -3052,8 +3069,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
goto same_page;
}
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
*nr_pages = remainder;
*position = vaddr;
@@ -3074,13 +3091,14 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
flush_cache_range(vma, address, end);
mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
- spin_lock(&mm->page_table_lock);
for (; address < end; address += huge_page_size(h)) {
- ptep = huge_pte_offset(mm, address);
+ spinlock_t *ptl;
+ ptep = huge_pte_offset_lock(mm, address, &ptl);
if (!ptep)
continue;
if (huge_pmd_unshare(mm, &address, ptep)) {
pages++;
+ spin_unlock(ptl);
continue;
}
if (!huge_pte_none(huge_ptep_get(ptep))) {
@@ -3090,8 +3108,8 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
set_huge_pte_at(mm, address, ptep, pte);
pages++;
}
+ spin_unlock(ptl);
}
- spin_unlock(&mm->page_table_lock);
/*
* Must flush TLB before releasing i_mmap_mutex: x86's huge_pmd_unshare
* may have cleared our pud entry and done put_page on the page table:
--
1.7.11.7
--
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