From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263325AbTLJB25 (ORCPT ); Tue, 9 Dec 2003 20:28:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263356AbTLJB25 (ORCPT ); Tue, 9 Dec 2003 20:28:57 -0500 Received: from ssatchell1.pyramid.net ([208.170.252.115]:21647 "EHLO ssatchell1.pyramid.net") by vger.kernel.org with ESMTP id S263325AbTLJB2x (ORCPT ); Tue, 9 Dec 2003 20:28:53 -0500 Subject: Re: Swap performance statistics in 2.6 -- which /proc file has it? From: Stephen Satchell To: Dominik Kubla Cc: linux-kernel@vger.kernel.org In-Reply-To: <3FD62845.8090301@kubla.de> References: <1070911748.2408.39.camel@dhcppc4> <3FD546D5.2000003@nishanet.com> <1070975964.5966.5.camel@ssatchell1.pyramid.net> <1070981185.6243.58.camel@ssatchell1.pyramid.net> <3FD62845.8090301@kubla.de> Content-Type: text/plain Message-Id: <1071019731.8045.31.camel@ssatchell1.pyramid.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 Date: Tue, 09 Dec 2003 17:28:51 -0800 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2003-12-09 at 11:53, Dominik Kubla wrote: > Richard B. Johnson wrote: > > If you need statistics v.s. time, you need to write an application > > that samples things at some fixed interval. In a previous life, > > I requested that "nr_free_pages()" be accessible from user-space, > > probably via /proc. That's all you need. Maybe that could be > > added now? In any event, samping free pages at some fixed-time > > interval should give you all the information you need. > > vmstat -a > sar -B > sar -r > > O'Reilly's "System Performance Tuning" might make for an interesting read, > especially pages 110ff (also its Linux informations are a bit out of date). How does sampling free pages give you an accurate measurement of swap activity? If I look at the free-page count at one-minute intervals, the system can, and WILL, inhale and exhale pages at a frightening clip, and there is no way I can see that sampling free-page count in a low-overhead way will do the trick. How does vmstat disk-swap activity? Looking at the source for vmstat in procps-2.0.11 I see how they do it for 2.4 kernels, but the part for 2.5 kernels doesn't seem to try to pick up swap statistics at all -- because there are none to get? (signed) Puzzled. (Why does this whole discussion remind me of the Firesign Theatre album _I Think We're All Bozos On This Bus_, and the question that Ah Clem asked: "Why does the porridge-bird lay his eggs in the air?")