Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754280Ab0KBBUM (ORCPT ); Mon, 1 Nov 2010 21:20:12 -0400 Received: from mga03.intel.com ([143.182.124.21]:39933 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750999Ab0KBBUK (ORCPT ); Mon, 1 Nov 2010 21:20:10 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.58,277,1286175600"; d="scan'208";a="343326239" Date: Tue, 2 Nov 2010 09:20:06 +0800 From: Wu Fengguang To: Dimitrios Apostolou Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: 2.6.36 io bring the system to its knees Message-ID: <20101102012006.GA3432@localhost> References: <20101031012224.GA8007@localhost> <20101031015132.GA10086@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 1265 Lines: 30 On Mon, Nov 01, 2010 at 01:09:34AM +0000, Dimitrios Apostolou wrote: > 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. 50% dirty ratio may help before the system goes thrashing (writing processes will be throttled less/later). However Aidar is seeing hours of unresponsiveness with heavy IO, in this case large dirty ratio won't help reduce the throttling any more. Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/