From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: [PATCH 11/47] writeback: reduce per-bdi dirty threshold ramp up time Date: Mon, 13 Dec 2010 14:43:00 +0800 Message-ID: <20101213064838.285412238@intel.com> References: <20101213064249.648862451@intel.com> Return-path: Received: from kanga.kvack.org ([205.233.56.17]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1PS2EQ-0005U4-A1 for glkm-linux-mm-2@m.gmane.org; Mon, 13 Dec 2010 07:49:58 +0100 Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 0AFF96B0093 for ; Mon, 13 Dec 2010 01:49:39 -0500 (EST) Content-Disposition: inline; filename=writeback-speedup-per-bdi-threshold-ramp-up.patch Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Jan Kara , Peter Zijlstra , Richard Kennedy , Wu Fengguang , Christoph Hellwig , Trond Myklebust , Dave Chinner , Theodore Ts'o , Chris Mason , Mel Gorman , Rik van Riel , KOSAKI Motohiro , Greg Thelen , Minchan Kim , linux-mm , linux-fsdevel@vger.kernel.org, LKML List-Id: linux-mm.kvack.org Reduce the dampening for the control system, yielding faster convergence. Currently it converges at a snail's pace for slow devices (in order of minutes). For really fast storage, the convergence speed should be fine. It makes sense to make it reasonably fast for typical desktops. After patch, it converges in ~10 seconds for 60MB/s writes and 4GB mem. So expect ~1s for a fast 600MB/s storage under 4GB mem, or ~4s under 16GB mem, which seems reasonable. $ while true; do grep BdiDirtyThresh /debug/bdi/8:0/stats; sleep 1; done BdiDirtyThresh: 0 kB BdiDirtyThresh: 118748 kB BdiDirtyThresh: 214280 kB BdiDirtyThresh: 303868 kB BdiDirtyThresh: 376528 kB BdiDirtyThresh: 411180 kB BdiDirtyThresh: 448636 kB BdiDirtyThresh: 472260 kB BdiDirtyThresh: 490924 kB BdiDirtyThresh: 499596 kB BdiDirtyThresh: 507068 kB ... DirtyThresh: 530392 kB CC: Peter Zijlstra CC: Richard Kennedy Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- linux-next.orig/mm/page-writeback.c 2010-12-08 22:44:25.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-12-08 22:44:25.000000000 +0800 @@ -125,7 +125,7 @@ static int calc_period_shift(void) else dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / 100; - return 2 + ilog2(dirty_total - 1); + return ilog2(dirty_total - 1) - 1; } /* -- 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