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mm: accelerate mm_populate() treatment of THP pages

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This change adds a follow_page_mask function which is equivalent to
follow_page, but with an extra page_mask argument.

follow_page_mask sets *page_mask to HPAGE_PMD_NR - 1 when it encounters
a THP page, and to 0 in other cases.

__get_user_pages() makes use of this in order to accelerate populating
THP ranges - that is, when both the pages and vmas arrays are NULL, we
don't need to iterate HPAGE_PMD_NR times to cover a single THP page (and
we also avoid taking mm->page_table_lock that many times).

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@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:
Michel Lespinasse 2013-02-22 16:35:56 -08:00 committed by Linus Torvalds
parent 28a35716d3
commit 240aadeedc
3 changed files with 38 additions and 12 deletions
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13
include/linux/mm.h
View file

@ -1629,8 +1629,17 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn);
struct page *follow_page(struct vm_area_struct *, unsigned long address,
unsigned int foll_flags);
struct page *follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int foll_flags,
unsigned int *page_mask);
static inline struct page *follow_page(struct vm_area_struct *vma,
unsigned long address, unsigned int foll_flags)
{
unsigned int unused_page_mask;
return follow_page_mask(vma, address, foll_flags, &unused_page_mask);
}
#define FOLL_WRITE 0x01 /* check pte is writable */
#define FOLL_TOUCH 0x02 /* mark page accessed */
#define FOLL_GET 0x04 /* do get_page on page */

31
mm/memory.c
View file

@ -1462,10 +1462,11 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
EXPORT_SYMBOL_GPL(zap_vma_ptes);
/**
* follow_page - look up a page descriptor from a user-virtual address
* follow_page_mask - look up a page descriptor from a user-virtual address
* @vma: vm_area_struct mapping @address
* @address: virtual address to look up
* @flags: flags modifying lookup behaviour
* @page_mask: on output, *page_mask is set according to the size of the page
*
* @flags can have FOLL_ flags set, defined in <linux/mm.h>
*
@ -1473,8 +1474,9 @@ EXPORT_SYMBOL_GPL(zap_vma_ptes);
* an error pointer if there is a mapping to something not represented
* by a page descriptor (see also vm_normal_page()).
*/
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
unsigned int flags)
struct page *follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags,
unsigned int *page_mask)
{
pgd_t *pgd;
pud_t *pud;
@ -1484,6 +1486,8 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
struct page *page;
struct mm_struct *mm = vma->vm_mm;
*page_mask = 0;
page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
if (!IS_ERR(page)) {
BUG_ON(flags & FOLL_GET);
@ -1530,6 +1534,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
page = follow_trans_huge_pmd(vma, address,
pmd, flags);
spin_unlock(&mm->page_table_lock);
*page_mask = HPAGE_PMD_NR - 1;
goto out;
}
} else
@ -1684,6 +1689,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
{
long i;
unsigned long vm_flags;
unsigned int page_mask;
if (!nr_pages)
return 0;
@ -1761,6 +1767,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
get_page(page);
}
pte_unmap(pte);
page_mask = 0;
goto next_page;
}
@ -1778,6 +1785,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
do {
struct page *page;
unsigned int foll_flags = gup_flags;
unsigned int page_increm;
/*
* If we have a pending SIGKILL, don't keep faulting
@ -1787,7 +1795,8 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
return i ? i : -ERESTARTSYS;
cond_resched();
while (!(page = follow_page(vma, start, foll_flags))) {
while (!(page = follow_page_mask(vma, start,
foll_flags, &page_mask))) {
int ret;
unsigned int fault_flags = 0;
@ -1861,13 +1870,19 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
flush_anon_page(vma, page, start);
flush_dcache_page(page);
page_mask = 0;
}
next_page:
if (vmas)
if (vmas) {
vmas[i] = vma;
i++;
start += PAGE_SIZE;
nr_pages--;
page_mask = 0;
}
page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
if (page_increm > nr_pages)
page_increm = nr_pages;
i += page_increm;
start += page_increm * PAGE_SIZE;
nr_pages -= page_increm;
} while (nr_pages && start < vma->vm_end);
} while (nr_pages);
return i;

6
mm/nommu.c
View file

@ -1819,9 +1819,11 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
return ret;
}
struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
unsigned int foll_flags)
struct page *follow_page_mask(struct vm_area_struct *vma,
unsigned long address, unsigned int flags,
unsigned int *page_mask)
{
*page_mask = 0;
return NULL;
}