Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759022Ab1FVVvc (ORCPT ); Wed, 22 Jun 2011 17:51:32 -0400 Received: from mail.betterlinux.com ([199.58.199.50]:42582 "EHLO mail.betterlinux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758919Ab1FVVva (ORCPT ); Wed, 22 Jun 2011 17:51:30 -0400 From: Andrea Righi To: Andrew Morton Cc: Minchan Kim , Rik van Riel , Peter Zijlstra , Johannes Weiner , KAMEZAWA Hiroyuki , Andrea Arcangeli , Hugh Dickins , Jerry James , Marcus Sorensen , Matt Heaton , linux-mm , LKML Subject: [PATCH RFC] fadvise: move active pages to inactive list with POSIX_FADV_DONTNEED Date: Wed, 22 Jun 2011 23:51:20 +0200 Message-Id: <1308779480-4950-1-git-send-email-andrea@betterlinux.com> X-Mailer: git-send-email 1.7.4.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4036 Lines: 103 There were some reported problems in the past about trashing page cache when a backup software (i.e., rsync) touches a huge amount of pages (see for example [1]). This problem has been almost fixed by the Minchan Kim's patch [2] and a proper use of fadvise() in the backup software. For example this patch set [3] has been proposed for inclusion in rsync. However, there can be still other similar trashing problems: when the backup software reads all the source files, some of them may be part of the actual working set of the system. When a posix_fadvise(POSIX_FADV_DONTNEED) is performed _all_ pages are evicted from pagecache, both the working set and the use-once pages touched only by the backup software. With the following solution when posix_fadvise(POSIX_FADV_DONTNEED) is called for an active page instead of removing it from the page cache it is added to the tail of the inactive list. Otherwise, if it's already in the inactive list the page is removed from the page cache. In this way if the backup was the only user of a page, that page will be immediately removed from the page cache by calling posix_fadvise(POSIX_FADV_DONTNEED). If the page was also touched by other processes it'll be moved to the inactive list, having another chance of being re-added to the working set, or simply reclaimed when memory is needed. Testcase: - create a 1GB file called "zero" - run md5sum zero to read all the pages in page cache (this is to simulate the user activity on this file) - run "rsync zero zero_copy" (rsync is patched with [3]) - re-run md5sum zero (user activity on the working set) and measure the time to complete this command The test has been performed using 3.0.0-rc4 vanilla and with this patch applied (3.0.0-rc4-fadvise). Results: avg elapsed time block:block_bio_queue 3.0.0-rc4 4.127s 8,214 3.0.0-rc4-fadvise 2.146s 0 In the first case the file is evicted from page cache completely and we must re-read it from the disk. In the second case the file is still in page cache (in the inactive list) and we don't need any other additional I/O operation. [1] http://marc.info/?l=rsync&m=128885034930933&w=2 [2] https://lkml.org/lkml/2011/2/20/57 [3] http://lists.samba.org/archive/rsync/2010-November/025827.html Signed-off-by: Andrea Righi --- mm/swap.c | 9 +++++---- mm/truncate.c | 5 ++++- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/swap.c b/mm/swap.c index 3a442f1..fc8bb76 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -411,10 +411,11 @@ void add_page_to_unevictable_list(struct page *page) * * 1. active, mapped page -> none * 2. active, dirty/writeback page -> inactive, head, PG_reclaim - * 3. inactive, mapped page -> none - * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim - * 5. inactive, clean -> inactive, tail - * 6. Others -> none + * 3. active, clean -> inactive, tail + * 4. inactive, mapped page -> none + * 5. inactive, dirty/writeback page -> inactive, head, PG_reclaim + * 6. inactive, clean -> inactive, tail + * 7. Others -> none * * In 4, why it moves inactive's head, the VM expects the page would * be write it out by flusher threads as this is much more effective diff --git a/mm/truncate.c b/mm/truncate.c index 3a29a61..043aabd 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -357,7 +357,10 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, if (lock_failed) continue; - ret = invalidate_inode_page(page); + if (PageActive(page)) + ret = 0; + else + ret = invalidate_inode_page(page); unlock_page(page); /* * Invalidation is a hint that the page is no longer -- 1.7.4.1 -- 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/