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authorNick Piggin <nickpiggin@yahoo.com.au>2006-01-06 00:11:12 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-06 08:33:27 -0800
commit9617d95e6e9ffd883cf90a89724fe60d7ab22f9a (patch)
tree67d555d34d931bd253fbc4959ffdb1e5b904f2b0
parent224abf92b2f439a9030f21d2926ec8047d1ffcdb (diff)
[PATCH] mm: rmap optimisation
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>
-rw-r--r--fs/exec.c2
-rw-r--r--include/linux/rmap.h1
-rw-r--r--mm/memory.c6
-rw-r--r--mm/rmap.c49
4 files changed, 43 insertions, 15 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 22533cce0611..e75a9548da8e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -324,7 +324,7 @@ void install_arg_page(struct vm_area_struct *vma,
lru_cache_add_active(page);
set_pte_at(mm, address, pte, pte_mkdirty(pte_mkwrite(mk_pte(
page, vma->vm_page_prot))));
- page_add_anon_rmap(page, vma, address);
+ page_add_new_anon_rmap(page, vma, address);
pte_unmap_unlock(pte, ptl);
/* no need for flush_tlb */
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 33261f1d2239..9d6fbeef2104 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -71,6 +71,7 @@ void __anon_vma_link(struct vm_area_struct *);
* rmap interfaces called when adding or removing pte of page
*/
void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
+void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void page_add_file_rmap(struct page *);
void page_remove_rmap(struct page *);
diff --git a/mm/memory.c b/mm/memory.c
index e249088908c4..d7ca7de10f4d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1498,7 +1498,7 @@ gotten:
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
lru_cache_add_active(new_page);
- page_add_anon_rmap(new_page, vma, address);
+ page_add_new_anon_rmap(new_page, vma, address);
/* Free the old page.. */
new_page = old_page;
@@ -1978,7 +1978,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
inc_mm_counter(mm, anon_rss);
lru_cache_add_active(page);
SetPageReferenced(page);
- page_add_anon_rmap(page, vma, address);
+ page_add_new_anon_rmap(page, vma, address);
} else {
/* Map the ZERO_PAGE - vm_page_prot is readonly */
page = ZERO_PAGE(address);
@@ -2109,7 +2109,7 @@ retry:
if (anon) {
inc_mm_counter(mm, anon_rss);
lru_cache_add_active(new_page);
- page_add_anon_rmap(new_page, vma, address);
+ page_add_new_anon_rmap(new_page, vma, address);
} else {
inc_mm_counter(mm, file_rss);
page_add_file_rmap(new_page);
diff --git a/mm/rmap.c b/mm/rmap.c
index f853c6def159..4107f64ff749 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -435,6 +435,26 @@ int page_referenced(struct page *page, int is_locked)
}
/**
+ * 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
* @vma: the vm area in which the mapping is added
@@ -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