From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: [PATCH 26/47] writeback: start background writeback earlier Date: Mon, 13 Dec 2010 14:43:15 +0800 Message-ID: <20101213064840.154570271@intel.com> References: <20101213064249.648862451@intel.com> Cc: Jan Kara , Wu Fengguang To: Andrew Morton Return-path: CC: Christoph Hellwig CC: Trond Myklebust CC: Dave Chinner CC: Theodore Ts'o CC: Chris Mason CC: Peter Zijlstra CC: Mel Gorman CC: Rik van Riel CC: KOSAKI Motohiro CC: Greg Thelen CC: Minchan Kim Cc: linux-mm Cc: Cc: LKML Content-Disposition: inline; filename=writeback-kick-background-early.patch Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org It's possible for some one to suddenly eat lots of memory, leading to sudden drop of global dirty limit. So a dirtier task may get hard throttled immediately without some previous balance_dirty_pages() call to invoke background writeback. In this case we need to check for background writeback earlier in the loop to avoid stucking the application for very long time. This was not a problem before the IO-less balance_dirty_pages() because it will try to write something and then break out of the loop regardless of the global limit. Another scheme this check will help is, the dirty limit is too close to the background threshold, so that someone manages to jump directly into the pause threshold (background+dirty)/2. Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 3 +++ 1 file changed, 3 insertions(+) --- linux-next.orig/mm/page-writeback.c 2010-12-08 23:54:36.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-12-08 23:56:55.000000000 +0800 @@ -662,6 +662,9 @@ static void balance_dirty_pages(struct a break; bdi_prev_dirty = bdi_dirty; + if (unlikely(!writeback_in_progress(bdi))) + bdi_start_background_writeback(bdi); + bdi_update_bandwidth(bdi, start_time, bdi_dirty, bdi_thresh); if (bdi_dirty >= task_thresh) { -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org