From ba9aa8399fda48510d80c2fed1afb8fedbe1bb41 Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Wed, 21 Jul 2010 20:32:30 -0600 Subject: writeback: the kupdate expire timestamp should be a moving target Dynamically compute the dirty expire timestamp at queue_io() time. writeback_control.older_than_this used to be determined at entrance to the kupdate writeback work. This _static_ timestamp may go stale if the kupdate work runs on and on. The flusher may then stuck with some old busy inodes, never considering newly expired inodes thereafter. This has two possible problems: - It is unfair for a large dirty inode to delay (for a long time) the writeback of small dirty inodes. - As time goes by, the large and busy dirty inode may contain only _freshly_ dirtied pages. Ignoring newly expired dirty inodes risks delaying the expired dirty pages to the end of LRU lists, triggering the evil pageout(). Nevertheless this patch merely addresses part of the problem. v2: keep policy changes inside wb_writeback() and keep the wbc.older_than_this visibility as suggested by Dave. CC: Dave Chinner Acked-by: Jan Kara Acked-by: Mel Gorman Signed-off-by: Itaru Kitayama Signed-off-by: Wu Fengguang --- fs/fs-writeback.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 271cf2150ba0..0adee7853b80 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -672,11 +672,6 @@ static long wb_writeback(struct bdi_writeback *wb, long write_chunk = MAX_WRITEBACK_PAGES; struct inode *inode; - if (wbc.for_kupdate) { - wbc.older_than_this = &oldest_jif; - oldest_jif = jiffies - - msecs_to_jiffies(dirty_expire_interval * 10); - } if (!wbc.range_cyclic) { wbc.range_start = 0; wbc.range_end = LLONG_MAX; @@ -723,6 +718,12 @@ static long wb_writeback(struct bdi_writeback *wb, if (work->for_background && !over_bground_thresh()) break; + if (work->for_kupdate) { + oldest_jif = jiffies - + msecs_to_jiffies(dirty_expire_interval * 10); + wbc.older_than_this = &oldest_jif; + } + wbc.more_io = 0; wbc.nr_to_write = write_chunk; wbc.pages_skipped = 0; -- cgit v1.2.3