From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Mon, 01 Sep 2008 22:54:47 -0700 (PDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m825shMI012905 for ; Mon, 1 Sep 2008 22:54:43 -0700 Received: from ipmail05.adl2.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 21F1B12FE216 for ; Mon, 1 Sep 2008 22:56:08 -0700 (PDT) Received: from ipmail05.adl2.internode.on.net (ipmail05.adl2.internode.on.net [203.16.214.145]) by cuda.sgi.com with ESMTP id jLTNWMJIkms7Dpxt for ; Mon, 01 Sep 2008 22:56:08 -0700 (PDT) Date: Tue, 2 Sep 2008 15:56:04 +1000 From: Dave Chinner Subject: Re: [PATCH] Tweak tracing allocation sizes Message-ID: <20080902055604.GD15962@disturbed> References: <48BCD3BE.5040107@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48BCD3BE.5040107@sgi.com> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Lachlan McIlroy Cc: xfs-dev , xfs-oss On Tue, Sep 02, 2008 at 03:48:46PM +1000, Lachlan McIlroy wrote: > The size of a single ktrace entry is 16 pointers so 128 bytes. For the case > of XFS_RW_KTRACE_SIZE which is 128 entries this equates to 16KB and on a system > with 4KB pages that is under memory pressure this can stall that process for a > significant time while it hunts for 4 free pages. Cutting this value back to > 32 means it will only need one page. That will effectively render that type of tracing useless - 32 entries is not enough history to capture enough read/write/map/invalidate trace events to be meaningful. In the past I've often had to increase this to 256 or 512 entries to be able to capture the events necessary to debug problems... Cheers, Dave. -- Dave Chinner david@fromorbit.com