Messages in this thread Patch in this message | | | Date | Mon, 6 Jun 2005 20:57:57 +0100 (BST) | From | Hugh Dickins <> | Subject | [PATCH 1/2] do_wp_page: cannot share file page |
| |
A small optimization to do_wp_page's check for whether to avoid copy by reusing the page already mapped. It can never share a cached file page, nor can it share a reserved page (often the empty zero page), so it's a waste of time to lock and unlock in those cases. Which nowadays can both be neatly excluded by a preliminary PageAnon test.
Christoph has reported that a preliminary page_count test proved valuable for scalability here, but PageAnon covers more common cases all at once.
Signed-off-by: Hugh Dickins <hugh@veritas.com> ---
mm/memory.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-)
--- 2.6.12-rc6/mm/memory.c 2005-05-25 18:09:21.000000000 +0100 +++ linux/mm/memory.c 2005-06-04 20:41:55.000000000 +0100 @@ -1264,7 +1264,7 @@ static int do_wp_page(struct mm_struct * } old_page = pfn_to_page(pfn); - if (!TestSetPageLocked(old_page)) { + if (PageAnon(old_page) && !TestSetPageLocked(old_page)) { int reuse = can_share_swap_page(old_page); unlock_page(old_page); if (reuse) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |