From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753733Ab0ILPzl (ORCPT ); Sun, 12 Sep 2010 11:55:41 -0400 Received: from mga11.intel.com ([192.55.52.93]:33603 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753419Ab0ILPzD (ORCPT ); Sun, 12 Sep 2010 11:55:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.56,355,1280732400"; d="scan'208";a="606204421" Message-Id: <20100912155204.602761236@intel.com> User-Agent: quilt/0.48-1 Date: Sun, 12 Sep 2010 23:49:58 +0800 From: Wu Fengguang To: linux-mm Cc: LKML , Peter Zijlstra , Richard Kennedy , "Martin J. Bligh" , Wu Fengguang CC: Andrew Morton CC: "Theodore Ts'o" CC: Dave Chinner CC: Jan Kara CC: Mel Gorman CC: Rik van Riel CC: KOSAKI Motohiro CC: Chris Mason CC: Christoph Hellwig CC: Li Shaohua Subject: [PATCH 13/17] writeback: reduce per-bdi dirty threshold ramp up time References: <20100912154945.758129106@intel.com> Content-Disposition: inline; filename=writeback-speedup-per-bdi-threshold-ramp-up.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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 looks good. $ 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 CC: Martin J. Bligh Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- linux-next.orig/mm/page-writeback.c 2010-08-30 10:24:00.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-08-30 10:27:10.000000000 +0800 @@ -131,7 +131,7 @@ 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; } /*