From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751448AbaAXX0J (ORCPT ); Fri, 24 Jan 2014 18:26:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42266 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750903AbaAXX0H (ORCPT ); Fri, 24 Jan 2014 18:26:07 -0500 Message-ID: <52E2F680.10409@redhat.com> Date: Fri, 24 Jan 2014 18:25:52 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Johannes Weiner , Andrew Morton CC: Tejun Heo , Mel Gorman , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 2/2] mm: page-writeback: do not count anon pages as dirtyable memory References: <1390600984-13925-1-git-send-email-hannes@cmpxchg.org> <1390600984-13925-3-git-send-email-hannes@cmpxchg.org> In-Reply-To: <1390600984-13925-3-git-send-email-hannes@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/24/2014 05:03 PM, Johannes Weiner wrote: > The VM is currently heavily tuned to avoid swapping. Whether that is > good or bad is a separate discussion, but as long as the VM won't swap > to make room for dirty cache, we can not consider anonymous pages when > calculating the amount of dirtyable memory, the baseline to which > dirty_background_ratio and dirty_ratio are applied. > > A simple workload that occupies a significant size (40+%, depending on > memory layout, storage speeds etc.) of memory with anon/tmpfs pages > and uses the remainder for a streaming writer demonstrates this > problem. In that case, the actual cache pages are a small fraction of > what is considered dirtyable overall, which results in an relatively > large portion of the cache pages to be dirtied. As kswapd starts > rotating these, random tasks enter direct reclaim and stall on IO. > > Only consider free pages and file pages dirtyable. > > Signed-off-by: Johannes Weiner Reviewed-by: Rik van Riel -- All rights reversed