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mm: accelerate munlock() treatment of THP pages

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munlock_vma_pages_range() was always incrementing addresses by PAGE_SIZE
at a time.  When munlocking THP pages (or the huge zero page), this
resulted in taking the mm->page_table_lock 512 times in a row.

We can do better by making use of the page_mask returned by
follow_page_mask (for the huge zero page case), or the size of the page
munlock_vma_page() operated on (for the true THP page case).

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 2013-02-27 17:02:44 -08:00 committed by Linus Torvalds
parent c5a51053cf
commit ff6a6da60b
2 changed files with 24 additions and 12 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
mm/internal.h
View file

@ -195,7 +195,7 @@ static inline int mlocked_vma_newpage(struct vm_area_struct *vma,
* must be called with vma's mmap_sem held for read or write, and page locked.
*/
extern void mlock_vma_page(struct page *page);
extern void munlock_vma_page(struct page *page);
extern unsigned int munlock_vma_page(struct page *page);
/*
* Clear the page's PageMlocked(). This can be useful in a situation where

34
mm/mlock.c
View file

@ -102,13 +102,16 @@ void mlock_vma_page(struct page *page)
* can't isolate the page, we leave it for putback_lru_page() and vmscan
* [page_referenced()/try_to_unmap()] to deal with.
*/
void munlock_vma_page(struct page *page)
unsigned int munlock_vma_page(struct page *page)
{
unsigned int page_mask = 0;
BUG_ON(!PageLocked(page));
if (TestClearPageMlocked(page)) {
mod_zone_page_state(page_zone(page), NR_MLOCK,
-hpage_nr_pages(page));
unsigned int nr_pages = hpage_nr_pages(page);
mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
page_mask = nr_pages - 1;
if (!isolate_lru_page(page)) {
int ret = SWAP_AGAIN;
@ -141,6 +144,8 @@ void munlock_vma_page(struct page *page)
count_vm_event(UNEVICTABLE_PGMUNLOCKED);
}
}
return page_mask;
}
/**
@ -159,7 +164,6 @@ long __mlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end, int *nonblocking)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long addr = start;
unsigned long nr_pages = (end - start) / PAGE_SIZE;
int gup_flags;
@ -189,7 +193,7 @@ long __mlock_vma_pages_range(struct vm_area_struct *vma,
* We made sure addr is within a VMA, so the following will
* not result in a stack expansion that recurses back here.
*/
return __get_user_pages(current, mm, addr, nr_pages, gup_flags,
return __get_user_pages(current, mm, start, nr_pages, gup_flags,
NULL, NULL, nonblocking);
}
@ -226,13 +230,12 @@ static int __mlock_posix_error_return(long retval)
void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
unsigned long addr;
lru_add_drain();
vma->vm_flags &= ~VM_LOCKED;
for (addr = start; addr < end; addr += PAGE_SIZE) {
while (start < end) {
struct page *page;
unsigned int page_mask, page_increm;
/*
* Although FOLL_DUMP is intended for get_dump_page(),
* it just so happens that its special treatment of the
@ -240,13 +243,22 @@ void munlock_vma_pages_range(struct vm_area_struct *vma,
* suits munlock very well (and if somehow an abnormal page
* has sneaked into the range, we won't oops here: great).
*/
page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
&page_mask);
if (page && !IS_ERR(page)) {
lock_page(page);
munlock_vma_page(page);
lru_add_drain();
/*
* Any THP page found by follow_page_mask() may have
* gotten split before reaching munlock_vma_page(),
* so we need to recompute the page_mask here.
*/
page_mask = munlock_vma_page(page);
unlock_page(page);
put_page(page);
}
page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
start += page_increm * PAGE_SIZE;
cond_resched();
}
}