Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269169AbUIHWWH (ORCPT ); Wed, 8 Sep 2004 18:22:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269183AbUIHWWH (ORCPT ); Wed, 8 Sep 2004 18:22:07 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.105]:23980 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S269169AbUIHWVw (ORCPT ); Wed, 8 Sep 2004 18:21:52 -0400 Date: Wed, 08 Sep 2004 15:20:42 -0700 From: "Martin J. Bligh" To: Diego Calleja cc: riel@redhat.com, raybry@sgi.com, marcelo.tosatti@cyclades.com, kernel@kolivas.org, akpm@osdl.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, piggin@cyberone.com.au Subject: Re: swapping and the value of /proc/sys/vm/swappiness Message-ID: <50520000.1094682042@flay> In-Reply-To: <20040908235503.3f01523a.diegocg@teleline.es> References: <5860000.1094664673@flay><20040908215008.10a56e2b.diegocg@teleline.es><36100000.1094677832@flay> <20040908235503.3f01523a.diegocg@teleline.es> X-Mailer: Mulberry/2.1.2 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2062 Lines: 38 >> I really don't see any point in pushing the self-tuning of the kernel out >> into userspace. What are you hoping to achieve? > > Well your own words explain it, I think. "it's all dependant on the workload", > which means that only the user knows what he is going to do with the machine > and that the kernel doesn't knows that, so the algoritms built in the kernel > may be "not perfect" in their auto-tuning job. The point would be to > be able to take decisions the kernel can't take because userspace would > know better how the system should behave, say stupids things like "I want > to have this set of tunables which make compile jobs 0.01% faster at 12:00 > because at that time a cron job autocompiles cvs snapshots of some project, > and at 6:00 those jobs have already finished so at that time I want a set > of tunables optimized for my everyday desktop work which make everthing 0.01% > slower but the system feels a 5% more reponsive". (well, for that a shell script > is enought) Kernel however could try to adapt itself to those changes, and do > it well...I don't really know. This came to my mind when I was thinking about > irqbalance case, which was somewhat similar, I also remember a discussion > about a "ktuned" in the mailing lists...I guess it's a matter of coding it > and get some numbers :-/ Oh, I see what you mean. I think we're much better off sticking the mechanism for autotuning stuff in the kernel - if we want to feed in policy from userspace (which 99.9% of people will never do), it can be through such things as /proc/sys/vm/swapiness ... that could just fix them statically if people insisted on such things. Having the kernel do something sensible by default is what we aim for ... overrides still are possible if the sysadmin really thinks they're smarter ;-) M. - 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/