Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752595Ab3JYJP0 (ORCPT ); Fri, 25 Oct 2013 05:15:26 -0400 Received: from exprod5og105.obsmtp.com ([64.18.0.180]:32824 "EHLO exprod5og105.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610Ab3JYJPZ (ORCPT ); Fri, 25 Oct 2013 05:15:25 -0400 Date: Fri, 25 Oct 2013 11:15:55 +0200 From: Karl Kiniger 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 Message-ID: <20131025091555.GA30895@kipc2.localdomain> References: <160824051.3072.1382685914055.JavaMail.mail@webmail07> <1814253454.3449.1382689853825.JavaMail.mail@webmail07> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-GEHealthcare-MailScanner: Found to be clean X-GEHealthcare-MailScanner-From: karl.kiniger@med.ge.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1580 Lines: 38 On Fri 131025, 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. > > The modern way of expressing the dirty limits are to give the actual > absolute byte amounts, but we default to the legacy ratio mode.. > > Linus Is it currently possible to somehow set above values per block device? I want default behaviour for almost everything but DVD drives in DVD+RW packet writing mode may easily take several minutes in case of a sync. Karl -- 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/