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rmap: add exclusively owned pages to the newest anon_vma

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The recent anon_vma fixes cause many anonymous pages to end up
in the parent process anon_vma, even when the page is exclusively
owned by the current process.

Adding exclusively owned anonymous pages to the top anon_vma
reduces rmap scanning overhead, especially in workloads with
forking servers.

This patch adds a parameter to __page_set_anon_rmap that can
be used to indicate whether or not the added page is exclusively
owned by the current process.

Pages added through page_add_new_anon_rmap are exclusively
owned by the current process, and can be added to the top
anon_vma.

Pages added through page_add_anon_rmap can be either shared
or exclusively owned, so we do the conservative thing and
add it to the oldest anon_vma.

A next step would be to add the exclusive parameter to
page_add_anon_rmap, to be used from functions where we do
know for sure whether a page is exclusively owned.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Lightly-tested-by: Borislav Petkov <bp@alien8.de>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
[ Edited to look nicer  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rik van Riel 2010-04-14 17:59:28 -04:00 committed by Linus Torvalds
parent 9b030e2006
commit e8a03feb54
1 changed files with 16 additions and 11 deletions
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27
mm/rmap.c
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@ -730,23 +730,28 @@ void page_move_anon_rmap(struct page *page,
* @page: the page to add the mapping to
* @vma: the vm area in which the mapping is added
* @address: the user virtual address mapped
* @exclusive: the page is exclusively owned by the current process
*/
static void __page_set_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
struct vm_area_struct *vma, unsigned long address, int exclusive)
{
struct anon_vma_chain *avc;
struct anon_vma *anon_vma;
struct anon_vma *anon_vma = vma->anon_vma;
BUG_ON(!vma->anon_vma);
BUG_ON(!anon_vma);
/*
* We must use the _oldest_ possible anon_vma for the page mapping!
* If the page isn't exclusively mapped into this vma,
* we must use the _oldest_ possible anon_vma for the
* page mapping!
*
* So take the last AVC chain entry in the vma, which is the deepest
* ancestor, and use the anon_vma from that.
* So take the last AVC chain entry in the vma, which is
* the deepest ancestor, and use the anon_vma from that.
*/
avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
anon_vma = avc->anon_vma;
if (!exclusive) {
struct anon_vma_chain *avc;
avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma);
anon_vma = avc->anon_vma;
}
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
@ -802,7 +807,7 @@ void page_add_anon_rmap(struct page *page,
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
if (first)
__page_set_anon_rmap(page, vma, address);
__page_set_anon_rmap(page, vma, address, 0);
else
__page_check_anon_rmap(page, vma, address);
}
@ -824,7 +829,7 @@ void page_add_new_anon_rmap(struct page *page,
SetPageSwapBacked(page);
atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
__inc_zone_page_state(page, NR_ANON_PAGES);
__page_set_anon_rmap(page, vma, address);
__page_set_anon_rmap(page, vma, address, 1);
if (page_evictable(page, vma))
lru_cache_add_lru(page, LRU_ACTIVE_ANON);
else