From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13696 invoked by alias); 8 May 2007 03:08:47 -0000 Received: (qmail 13684 invoked by uid 22791); 8 May 2007 03:08:46 -0000 X-Spam-Status: No, hits=0.6 required=5.0 tests=BAYES_50,DK_SIGNED,SARE_MSGID_LONG40,SPF_PASS X-Spam-Check-By: sourceware.org Received: from ug-out-1314.google.com (HELO ug-out-1314.google.com) (66.249.92.175) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 08 May 2007 03:08:43 +0000 Received: by ug-out-1314.google.com with SMTP id m3so75945uge for ; Mon, 07 May 2007 20:08:40 -0700 (PDT) DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=licMBSx69OIO4zScJthaU+TWHCJAYYGZsnWpdl4ecja6REMSqJMnrSn7/C85PH/bJcHX78xuacGAEaEvTUqlXe3CpgNcQNnIY8yRFeAnJMxRpFVP3Uj6pOxcwIY4fw9XcgPffrSsqHtQBafWyphllSD36vwhPF1R3lNHFYEQosg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=T/WPOa5dD9aKz+f+2wwwEDUKci4HUuERcX9ko6YNvN/3e21udPsDkw0fY1OVa0jE3nSatQCMTQFBnYzdW4W27qQPhdR3OrqiGloa1bI1mRcOwamjcUU4zjirJexnTvlJZviLpGeg7i/nN4W15ISjWortzsi//BySPOa5u9r/z3s= Received: by 10.67.30.6 with SMTP id h6mr137408ugj.1178593720759; Mon, 07 May 2007 20:08:40 -0700 (PDT) Received: by 10.67.64.14 with HTTP; Mon, 7 May 2007 20:08:40 -0700 (PDT) Message-ID: Date: Tue, 08 May 2007 03:08:00 -0000 From: "Jun Koi" To: "William Cohen" Subject: Re: Tracking vm activity Cc: SystemTAP In-Reply-To: <462D1F8B.4020607@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <462D1F8B.4020607@redhat.com> X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2007-q2/txt/msg00214.txt.bz2 On 4/24/07, William Cohen wrote: > Hi, > > I am playing around with getting information about page faults and I noticed > that there is a probe alias for the entry for the pagefault code. However, there > is no matching probe point for the return. It is useful to look at the return > value to determine what kind of page fault occurred (major or minor). The > attached patch provides a similar probe point for the return point. any comments > on the patch? > > This would be useful for the following senario. A probe on vm.pagefault could > get the address and a probe on vm.pagefault.return could get information how it > was handled. The analysis could then do things like which addresses cause major > page faults (real disk accesses). One could write out a log of the major page > faults (and the mmap operations) and track which files caused the page faults. > Probably don't want to walk through the mm structures when taking a page fault > to determine which file it came from. > Hi Will, I found this idea interesting. However, what do you think if the machine is SMP, or kernel is preemptive capable? Just imagine a scenario like this with 2 kernel threads A and B: - A causes page fault, then enters page fault handler (1) - B preempts A, causes fault, then enters page fault handler (2) - A exits page fault handler (3) - B exits page fault handler (4) In this case, you get the exit value at (3), but it is not relevant to the parameters collected in the above step (2). I cannot figure out how to correlate "enter" and "exit" function events in SMP or preemptive case. Any idea? Thanks, Jun