From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752704Ab0H0Kge (ORCPT ); Fri, 27 Aug 2010 06:36:34 -0400 Received: from mga03.intel.com ([143.182.124.21]:60590 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752168Ab0H0Kgc (ORCPT ); Fri, 27 Aug 2010 06:36:32 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.56,278,1280732400"; d="scan'208";a="317823442" Date: Fri, 27 Aug 2010 18:36:03 +0800 From: Wu Fengguang To: Andrew Morton Cc: KOSAKI Motohiro , Neil Brown , Con Kolivas , Jan Kara , Rik van Riel , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "david@fromorbit.com" , "hch@lst.de" , "axboe@kernel.dk" Subject: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio Message-ID: <20100827103603.GB6237@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%. This is not a user expected behavior. And it's inconsistent with calc_period_shift(), which uses the plain vm_dirty_ratio value. Let's rip the internal bound. At the same time, fix balance_dirty_pages() to work with the dirty_thresh=0 case. This allows applications to proceed when dirty+writeback pages are all cleaned. And ">" fits with the name "exceeded" better than ">=" does. Neil think it is an aesthetic improvement as well as a functional one :) CC: Jan Kara CC: Rik van Riel CC: Peter Zijlstra Proposed-by: Con Kolivas Reviewed-by: Neil Brown Reviewed-by: KOSAKI Motohiro Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) --- linux-next.orig/mm/page-writeback.c 2010-08-26 08:37:31.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-08-26 08:37:55.000000000 +0800 @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long * if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); - else { - int dirty_ratio; - - dirty_ratio = vm_dirty_ratio; - if (dirty_ratio < 5) - dirty_ratio = 5; - dirty = (dirty_ratio * available_memory) / 100; - } + else + dirty = (vm_dirty_ratio * available_memory) / 100; if (dirty_background_bytes) background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); @@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a * the last resort safeguard. */ dirty_exceeded = - (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) - || (nr_reclaimable + nr_writeback >= dirty_thresh); + (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh) + || (nr_reclaimable + nr_writeback > dirty_thresh); if (!dirty_exceeded) break;