Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753490Ab3JYL2c (ORCPT ); Fri, 25 Oct 2013 07:28:32 -0400 Received: from mail.lang.hm ([64.81.33.126]:38450 "EHLO bifrost.lang.hm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752305Ab3JYL2b (ORCPT ); Fri, 25 Oct 2013 07:28:31 -0400 Date: Fri, 25 Oct 2013 04:28:27 -0700 (PDT) From: David Lang X-X-Sender: dlang@asgard.lang.hm To: Linus Torvalds cc: "Artem S. Tashkinov" , Wu Fengguang , Andrew Morton , Linux Kernel Mailing List Subject: Re: Disabling in-memory write cache for x86-64 in Linux II In-Reply-To: Message-ID: References: <160824051.3072.1382685914055.JavaMail.mail@webmail07> <1814253454.3449.1382689853825.JavaMail.mail@webmail07> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 32 On Fri, 25 Oct 2013, Linus Torvalds wrote: > On Fri, Oct 25, 2013 at 9:30 AM, Artem S. Tashkinov wrote: >> >> My feeling is that vm.dirty_ratio/vm.dirty_background_ratio should _not_ be >> percentage based, 'cause for PCs/servers with a lot of memory (say 64GB or >> more) this value becomes unrealistic (13GB) and I've already had some >> unpleasant effects due to it. > > Right. The percentage notion really goes back to the days when we > typically had 8-64 *megabytes* of memory So if you had a 8MB machine > you wouldn't want to have more than one megabyte of dirty data, but if > you were "Mr Moneybags" and could afford 64MB, you might want to have > up to 8MB dirty!! > > Things have changed. > > So I would suggest we change the defaults. Or pwehaps make the rule be > that "the ratio numbers are 'ratio of memory up to 1GB'", to make the > semantics similar across 32-bit HIGHMEM machines and 64-bit machines. If you go this direction, allow ratios larger than 100%, some people may be willing to have huge amounts of dirty data on large memory machines (if the load is extremely bursty, they don't have other needs for I/O, or they have a very fast storage system, as a few examples) David Lang -- 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/