From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19866 invoked by alias); 22 Nov 2005 15:12:47 -0000 Received: (qmail 19857 invoked by uid 22791); 22 Nov 2005 15:12:46 -0000 X-Spam-Status: No, hits=-2.1 required=5.0 tests=AWL,BAYES_00,DNS_FROM_RFC_ABUSE X-Spam-Check-By: sourceware.org Received: from e36.co.us.ibm.com (HELO e36.co.us.ibm.com) (32.97.110.154) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 22 Nov 2005 15:12:44 +0000 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e36.co.us.ibm.com (8.12.11/8.12.11) with ESMTP id jAMFCgaR008964 for ; Tue, 22 Nov 2005 10:12:42 -0500 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.12.10/NCO/VERS6.8) with ESMTP id jAMFE3OW094948 for ; Tue, 22 Nov 2005 08:14:04 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11/8.13.3) with ESMTP id jAMFCfqJ031768 for ; Tue, 22 Nov 2005 08:12:42 -0700 Received: from tut.ibm.com.us.ibm.com (sig-9-65-126-145.mts.ibm.com [9.65.126.145]) by d03av02.boulder.ibm.com (8.12.11/8.12.11) with ESMTP id jAMFCVms031202; Tue, 22 Nov 2005 08:12:40 -0700 From: Tom Zanussi MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17283.13647.856527.25948@tut.ibm.com> Date: Tue, 22 Nov 2005 15:12:00 -0000 To: Mathieu Desnoyers Cc: "Stone, Joshua I" , Tom Zanussi , michel.dagenais@polymtl.ca, systemtap@sources.redhat.com Subject: Re: double fault -> PAGE_KERNEL flagged memory In-Reply-To: <20051122140021.GA3907@Krystal> References: <20051122140021.GA3907@Krystal> X-Mailer: VM 7.19 under 21.4 (patch 15) "Security Through Obscurity" XEmacs Lucid X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2005-q4/txt/msg00232.txt.bz2 Mathieu Desnoyers writes: > I suspect that your double fault may come from the systemTAP logging code. Do > you have an instrumentation point in any fault handler ? > > For Tom : can you flag the RelayFS buffer memory PAGE_KERNEL instead of > GFP_KERNEL ? Otherwise, it leads to page faults when accessing those pages when > accessed for the first time (seen with LTTng). It already is PAGE_KERNEL. The page faults you see with relayfs are vmalloc page faults i.e. minor faults that just update the kernel part of the current process's page table with the buffer pages. Anyway, systemtap doesn't use relayfs unless -b (bulk) is specified on the command line, so unless that's the case, it can't be relayfs causing the problem. tom