Commit e8a03feb authored by Rik van Riel's avatar Rik van Riel Committed by Linus Torvalds
Browse files

rmap: add exclusively owned pages to the newest anon_vma 



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: default avatarRik van Riel <riel@redhat.com>
Reviewed-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Lightly-tested-by: default avatarBorislav Petkov <bp@alien8.de>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
[ Edited to look nicer  - Linus ]
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9b030e20

mm/rmap.c

+16 −11
Original line number Diff line number Diff line
@@ -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.

	 */

	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

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