From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752583AbWCQK3N (ORCPT ); Fri, 17 Mar 2006 05:29:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752584AbWCQK3N (ORCPT ); Fri, 17 Mar 2006 05:29:13 -0500 Received: from mail22.syd.optusnet.com.au ([211.29.133.160]:60907 "EHLO mail22.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S1752583AbWCQK3M (ORCPT ); Fri, 17 Mar 2006 05:29:12 -0500 From: Con Kolivas To: "Pradeep Vincent" Subject: Re: Priority in Memory management Date: Fri, 17 Mar 2006 21:29:01 +1100 User-Agent: KMail/1.9.1 Cc: linux-kernel@vger.kernel.org References: <9fda5f510603170037v41d273c5naf36776e6f03246e@mail.gmail.com> In-Reply-To: <9fda5f510603170037v41d273c5naf36776e6f03246e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200603172129.01490.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Friday 17 March 2006 19:37, Pradeep Vincent wrote: > I tried searching for discussions related to this but in vain A > significant number of servers running Linux come under the category of > "Caching Servers". These servers usually try to server data either > from RAM or disk sub-systems and for obvious reasons want to serve as > much data as possible from RAM. Even if the dataset is comparable to > RAM size, other bon-performance critical activities on the system > (such as logging, log rotation/compression, remote performance > monitors, application code updates, security related searches ) > disturb the cache hit ratio. > > Mlocking the dataset is one option. Using fadvise/O_STREAM for > everything else is another option - but this doesn't address all the > cases. > > Instead of locking out all memory, being able to set priorities for > virtual memory regions comes across as a better idea. This way if the > system really really needs memory, kernel can reclaim the cache pages > but not just because somebody is writing something and it might seem > fair to reclaim the dataset cache. > > > Has this come up in the past. Any history at all - I am all ears for > ideas and concerns. True priority support in the form of a "vm scheduler" is something I've mentioned many times in the past. The overhead would not be insignificant. Nonetheless I do have some weak priority support for page reclaiming in my -ck tree because doing so was not overly expensive. As far as I'm aware noone is currently working on a comprehensive vm scheduler. Cheers, Con