From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753495Ab0KAUZI (ORCPT ); Mon, 1 Nov 2010 16:25:08 -0400 Received: from lo.gmane.org ([80.91.229.12]:60184 "EHLO lo.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753130Ab0KAUZF (ORCPT ); Mon, 1 Nov 2010 16:25:05 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Dimitrios Apostolou Subject: Re: 2.6.36 io bring the system to its knees Date: Mon, 1 Nov 2010 01:09:34 +0000 (UTC) Message-ID: References: <20101031012224.GA8007@localhost> <20101031015132.GA10086@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: 178-14-100.dynamic.cyta.gr User-Agent: Pan/0.133 (House of Butterflies) Cc: linux-mm@kvack.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Sun, 31 Oct 2010 09:51:32 +0800, Wu Fengguang wrote: > It may also help to lower the dirty ratio. > > echo 5 > /proc/sys/vm/dirty_ratio > > Memory pressure + heavy write can easily hurt responsiveness. > > - eats up to 20% (the default value for dirty_ratio) memory with dirty > pages and hence increase the memory pressure and number of swap IO My experience has been different with that. Wouldn't it make more sense to _increase_ dirty_ratio (to 50 lets say) and at the same time decrease dirty_background_ratio? That way writing to disk starts early, but the related apps stall waiting for I/O only when dirty_ratio is reached. Thanks, Dimitris > > - the file copy makes the device write congested and hence makes > pageout() easily blocked in get_request_wait() > > As a result every application may be slowed down by the heavy swap IO > when page fault as well as being blocked when allocating memory (which > may go into direct reclaim and then call pageout()). > > Thanks, > Fengguang