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[PATCH] mm: rmap optimisation

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Optimise rmap functions by minimising atomic operations when we know there
will be no concurrent modifications.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-01-06 00:11:12 -08:00 • committed by Linus Torvalds
parent 224abf92b2
commit 9617d95e6e
4 changed files with 43 additions and 15 deletions
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49
mm/rmap.c
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@ -434,6 +434,26 @@ int page_referenced(struct page *page, int is_locked)
return referenced;
}
/**
* page_set_anon_rmap - setup new anonymous rmap
* @page: the page to add the mapping to
* @vma: the vm area in which the mapping is added
* @address: the user virtual address mapped
*/
static void __page_set_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
struct anon_vma *anon_vma = vma->anon_vma;
BUG_ON(!anon_vma);
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
page->index = linear_page_index(vma, address);
inc_page_state(nr_mapped);
}
/**
* page_add_anon_rmap - add pte mapping to an anonymous page
* @page: the page to add the mapping to
@ -445,20 +465,27 @@ int page_referenced(struct page *page, int is_locked)
void page_add_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
if (atomic_inc_and_test(&page->_mapcount)) {
struct anon_vma *anon_vma = vma->anon_vma;
BUG_ON(!anon_vma);
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
page->index = linear_page_index(vma, address);
inc_page_state(nr_mapped);
}
if (atomic_inc_and_test(&page->_mapcount))
__page_set_anon_rmap(page, vma, address);
/* else checking page index and mapping is racy */
}
/*
* page_add_new_anon_rmap - add pte mapping to a new anonymous 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
*
* Same as page_add_anon_rmap but must only be called on *new* pages.
* This means the inc-and-test can be bypassed.
*/
void page_add_new_anon_rmap(struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
__page_set_anon_rmap(page, vma, address);
}
/**
* page_add_file_rmap - add pte mapping to a file page
* @page: the page to add the mapping to