From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752099AbaJOUFq (ORCPT ); Wed, 15 Oct 2014 16:05:46 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36649 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbaJOUFo (ORCPT ); Wed, 15 Oct 2014 16:05:44 -0400 Date: Wed, 15 Oct 2014 13:05:44 -0700 From: Andrew Morton To: Jamie Liu Cc: Johannes Weiner , Mel Gorman , Greg Thelen , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: vmscan: count only dirty pages as congested Message-Id: <20141015130544.380aca0acfcb1413459520b0@linux-foundation.org> In-Reply-To: <1413403115-1551-1-git-send-email-jamieliu@google.com> References: <1413403115-1551-1-git-send-email-jamieliu@google.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 15 Oct 2014 12:58:35 -0700 Jamie Liu wrote: > shrink_page_list() counts all pages with a mapping, including clean > pages, toward nr_congested if they're on a write-congested BDI. > shrink_inactive_list() then sets ZONE_CONGESTED if nr_dirty == > nr_congested. Fix this apples-to-oranges comparison by only counting > pages for nr_congested if they count for nr_dirty. > > ... > > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -875,7 +875,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, > * end of the LRU a second time. > */ > mapping = page_mapping(page); > - if ((mapping && bdi_write_congested(mapping->backing_dev_info)) || > + if (((dirty || writeback) && mapping && > + bdi_write_congested(mapping->backing_dev_info)) || > (writeback && PageReclaim(page))) > nr_congested++; What are the observed runtime effects of this change?