path: root/mm
diff options
authorKen Chen <kenchen@google.com>2007-02-10 01:43:15 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-11 10:51:19 -0800
commit767193253bbac889e176f90b6f17b7015f986551 (patch)
treea81c5c90d14c7892e6d7adb0432f4dff4ca3f906 /mm
parent[PATCH] zoneid: fix up calculations for ZONEID_PGSHIFT (diff)
[PATCH] simplify shmem_aops.set_page_dirty() method
shmem backed file does not have page writeback, nor it participates in backing device's dirty or writeback accounting. So using generic __set_page_dirty_nobuffers() for its .set_page_dirty aops method is a bit overkill. It unnecessarily prolongs shm unmap latency. For example, on a densely populated large shm segment (sevearl GBs), the unmapping operation becomes painfully long. Because at unmap, kernel transfers dirty bit in PTE into page struct and to the radix tree tag. The operation of tagging the radix tree is particularly expensive because it has to traverse the tree from the root to the leaf node on every dirty page. What's bothering is that radix tree tag is used for page write back. However, shmem is memory backed and there is no page write back for such file system. And in the end, we spend all that time tagging radix tree and none of that fancy tagging will be used. So let's simplify it by introduce a new aops __set_page_dirty_no_writeback and this will speed up shm unmap. Signed-off-by: Ken Chen <kenchen@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
2 files changed, 11 insertions, 1 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index be0efbde4994..438833cbbca4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -737,6 +737,16 @@ int write_one_page(struct page *page, int wait)
+ * For address_spaces which do not use buffers nor write back.
+ */
+int __set_page_dirty_no_writeback(struct page *page)
+ if (!PageDirty(page))
+ SetPageDirty(page);
+ return 0;
* For address_spaces which do not use buffers. Just tag the page as dirty in
* its radix tree.
diff --git a/mm/shmem.c b/mm/shmem.c
index 70da7a0981bf..b38e17169271 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2316,7 +2316,7 @@ static void destroy_inodecache(void)
static const struct address_space_operations shmem_aops = {
.writepage = shmem_writepage,
- .set_page_dirty = __set_page_dirty_nobuffers,
+ .set_page_dirty = __set_page_dirty_no_writeback,
.prepare_write = shmem_prepare_write,
.commit_write = simple_commit_write,