Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756295AbXJBJEX (ORCPT ); Tue, 2 Oct 2007 05:04:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754152AbXJBJDH (ORCPT ); Tue, 2 Oct 2007 05:03:07 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:39113 "HELO ustc.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1752456AbXJBJDA (ORCPT ); Tue, 2 Oct 2007 05:03:00 -0400 Message-ID: <391315778.00442@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20071002090254.987182999@mail.ustc.edu.cn> References: <20071002084143.110486039@mail.ustc.edu.cn> User-Agent: quilt/0.46-1 Date: Tue, 02 Oct 2007 16:41:48 +0800 From: Fengguang Wu To: Andrew Morton Cc: linux-kernel@vger.kernel.org, David Chinner , Ken Chen , Andrew Morton Cc: Michael Rubin Subject: [PATCH 5/5] writeback: introduce writeback_control.more_io to indicate more io Content-Disposition: inline; filename=writeback-more-data.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4136 Lines: 108 After making dirty a 100M file, the normal behavior is to start the writeback for all data after 30s delays. But sometimes the following happens instead: - after 30s: ~4M - after 5s: ~4M - after 5s: all remaining 92M Some analyze shows that the internal io dispatch queues goes like this: s_io s_more_io ------------------------- 1) 100M,1K 0 2) 1K 96M 3) 0 96M 1) initial state with a 100M file and a 1K file 2) 4M written, nr_to_write <= 0, so write more 3) 1K written, nr_to_write > 0, no more writes(BUG) nr_to_write > 0 in (3) fools the upper layer to think that data have all been written out. The big dirty file is actually still sitting in s_more_io. We cannot simply splice s_more_io back to s_io as soon as s_io becomes empty, and let the loop in generic_sync_sb_inodes() continue: this may starve newly expired inodes in s_dirty. It is also not an option to draw inodes from both s_more_io and s_dirty, an let the loop go on: this might lead to live locks, and might also starve other superblocks in sync time(well kupdate may still starve some superblocks, that's another bug). We have to return when a full scan of s_io completes. So nr_to_write > 0 does not necessarily mean that "all data are written". This patch introduces a flag writeback_control.more_io to indicate this situation. With it the big dirty file no longer has to wait for the next kupdate invocation 5s later. Cc: David Chinner Cc: Ken Chen Cc: Andrew Morton Signed-off-by: Fengguang Wu --- fs/fs-writeback.c | 2 ++ include/linux/writeback.h | 1 + mm/page-writeback.c | 9 ++++++--- 3 files changed, 9 insertions(+), 3 deletions(-) --- linux-2.6.23-rc8-mm2.orig/include/linux/writeback.h +++ linux-2.6.23-rc8-mm2/include/linux/writeback.h @@ -62,6 +62,7 @@ struct writeback_control { unsigned for_reclaim:1; /* Invoked from the page allocator */ unsigned for_writepages:1; /* This is a writepages() call */ unsigned range_cyclic:1; /* range_start is cyclic */ + unsigned more_io:1; /* more io to be dispatched */ void *fs_private; /* For use by ->writepages() */ }; --- linux-2.6.23-rc8-mm2.orig/fs/fs-writeback.c +++ linux-2.6.23-rc8-mm2/fs/fs-writeback.c @@ -487,6 +487,8 @@ int generic_sync_sb_inodes(struct super_ if (wbc->nr_to_write <= 0) break; } + if (!list_empty(&sb->s_more_io)) + wbc->more_io = 1; spin_unlock(&inode_lock); return ret; /* Leave any unwritten inodes on s_io */ --- linux-2.6.23-rc8-mm2.orig/mm/page-writeback.c +++ linux-2.6.23-rc8-mm2/mm/page-writeback.c @@ -553,6 +553,7 @@ static void background_writeout(unsigned global_page_state(NR_UNSTABLE_NFS) < background_thresh && min_pages <= 0) break; + wbc.more_io = 0; wbc.encountered_congestion = 0; wbc.nr_to_write = MAX_WRITEBACK_PAGES; wbc.pages_skipped = 0; @@ -560,8 +561,9 @@ static void background_writeout(unsigned min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { /* Wrote less than expected */ - congestion_wait(WRITE, HZ/10); - if (!wbc.encountered_congestion) + if (wbc.encountered_congestion || wbc.more_io) + congestion_wait(WRITE, HZ/10); + else break; } } @@ -626,11 +628,12 @@ static void wb_kupdate(unsigned long arg global_page_state(NR_UNSTABLE_NFS) + (inodes_stat.nr_inodes - inodes_stat.nr_unused); while (nr_to_write > 0) { + wbc.more_io = 0; wbc.encountered_congestion = 0; wbc.nr_to_write = MAX_WRITEBACK_PAGES; writeback_inodes(&wbc); if (wbc.nr_to_write > 0) { - if (wbc.encountered_congestion) + if (wbc.encountered_congestion || wbc.more_io) congestion_wait(WRITE, HZ/10); else break; /* All the old data is written */ -- - 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/