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thp: implement split_huge_pmd()

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Original split_huge_page() combined two operations: splitting PMDs into
tables of PTEs and splitting underlying compound page.  This patch
implements split_huge_pmd() which split given PMD without splitting
other PMDs this page mapped with or underlying compound page.

Without tail page refcounting, implementation of split_huge_pmd() is
pretty straight-forward.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-01-15 16:53:53 -08:00 committed by Linus Torvalds
parent e81c48024f
commit eef1b3ba05
2 changed files with 134 additions and 1 deletions
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11
include/linux/huge_mm.h
View File

@ -92,7 +92,16 @@ extern unsigned long transparent_hugepage_flags;
#define split_huge_page_to_list(page, list) BUILD_BUG()
#define split_huge_page(page) BUILD_BUG()
#define split_huge_pmd(__vma, __pmd, __address) BUILD_BUG()
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address);
#define split_huge_pmd(__vma, __pmd, __address) \
do { \
pmd_t *____pmd = (__pmd); \
if (pmd_trans_huge(*____pmd)) \
__split_huge_pmd(__vma, __pmd, __address); \
} while (0)
#if HPAGE_PMD_ORDER >= MAX_ORDER
#error "hugepages can't be allocated by the buddy allocator"

124
mm/huge_memory.c
View File

@ -2666,6 +2666,130 @@ static int khugepaged(void *none)
return 0;
}
static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd)
{
struct mm_struct *mm = vma->vm_mm;
pgtable_t pgtable;
pmd_t _pmd;
int i;
/* leave pmd empty until pte is filled */
pmdp_huge_clear_flush_notify(vma, haddr, pmd);
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t *pte, entry;
entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
entry = pte_mkspecial(entry);
pte = pte_offset_map(&_pmd, haddr);
VM_BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
pte_unmap(pte);
}
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
put_huge_zero_page();
}
static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long haddr)
{
struct mm_struct *mm = vma->vm_mm;
struct page *page;
pgtable_t pgtable;
pmd_t _pmd;
bool young, write;
int i;
VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
VM_BUG_ON(!pmd_trans_huge(*pmd));
count_vm_event(THP_SPLIT_PMD);
if (vma_is_dax(vma)) {
pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
if (is_huge_zero_pmd(_pmd))
put_huge_zero_page();
return;
} else if (is_huge_zero_pmd(*pmd)) {
return __split_huge_zero_page_pmd(vma, haddr, pmd);
}
page = pmd_page(*pmd);
VM_BUG_ON_PAGE(!page_count(page), page);
atomic_add(HPAGE_PMD_NR - 1, &page->_count);
write = pmd_write(*pmd);
young = pmd_young(*pmd);
/* leave pmd empty until pte is filled */
pmdp_huge_clear_flush_notify(vma, haddr, pmd);
pgtable = pgtable_trans_huge_withdraw(mm, pmd);
pmd_populate(mm, &_pmd, pgtable);
for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
pte_t entry, *pte;
/*
* Note that NUMA hinting access restrictions are not
* transferred to avoid any possibility of altering
* permissions across VMAs.
*/
entry = mk_pte(page + i, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (!write)
entry = pte_wrprotect(entry);
if (!young)
entry = pte_mkold(entry);
pte = pte_offset_map(&_pmd, haddr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
atomic_inc(&page[i]._mapcount);
pte_unmap(pte);
}
/*
* Set PG_double_map before dropping compound_mapcount to avoid
* false-negative page_mapped().
*/
if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
for (i = 0; i < HPAGE_PMD_NR; i++)
atomic_inc(&page[i]._mapcount);
}
if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
/* Last compound_mapcount is gone. */
__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
if (TestClearPageDoubleMap(page)) {
/* No need in mapcount reference anymore */
for (i = 0; i < HPAGE_PMD_NR; i++)
atomic_dec(&page[i]._mapcount);
}
}
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
}
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address)
{
spinlock_t *ptl;
struct mm_struct *mm = vma->vm_mm;
unsigned long haddr = address & HPAGE_PMD_MASK;
mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
ptl = pmd_lock(mm, pmd);
if (likely(pmd_trans_huge(*pmd)))
__split_huge_pmd_locked(vma, pmd, haddr);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
}
static void split_huge_pmd_address(struct vm_area_struct *vma,
unsigned long address)
{