From owner-freebsd-current@FreeBSD.ORG  Fri May 26 20:03:28 2006
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: current@freebsd.org
Delivered-To: freebsd-current@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 0DA1616A8CD
	for <current@freebsd.org>; Fri, 26 May 2006 20:03:28 +0000 (UTC)
	(envelope-from jb@what-creek.com)
Received: from what-creek.com (what-creek.com [66.111.37.70])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 528FF43D62
	for <current@freebsd.org>; Fri, 26 May 2006 20:03:24 +0000 (GMT)
	(envelope-from jb@what-creek.com)
Received: by what-creek.com (Postfix, from userid 102)
	id 2618C78C1D; Fri, 26 May 2006 20:03:23 +0000 (GMT)
Date: Fri, 26 May 2006 20:03:22 +0000
From: John Birrell <jb@what-creek.com>
To: Joseph Koshy <joseph.koshy@gmail.com>
Message-ID: <20060526200322.GC34554@what-creek.com>
References: <20060525065510.GA20475@what-creek.com>
	<m264jt2mjw.wl%gnn@neville-neil.com>
	<84dead720605260818t7460cd6dp5de7311a1b5edc28@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <84dead720605260818t7460cd6dp5de7311a1b5edc28@mail.gmail.com>
User-Agent: Mutt/1.4.2.1i
Cc: current@freebsd.org
Subject: Re: DTrace for FreeBSD - Status Update
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 26 May 2006 20:03:36 -0000

On Fri, May 26, 2006 at 08:48:21PM +0530, Joseph Koshy wrote:
> >But, I have a naive question.  Should this be integrated in
> >some way with the hwpmc work of Joseph Koshy since I think it
> >could be useful for DTRace to get information from the CPU as
> >well.
> 
> Disclaimer: I've only just started reading about DTrace.
> 
> There appear to be two ways to integrate hwpmc and DTrace:
> 
> - Augment the D virtual machine with a primitive that can
>   read PMC values (e.g.- using RDPMC or RDMSR instructions
>   on x86 CPUs).  Make this primitive available
>   to scripts for allocating and reading from PMCs (say
>   a "pmcread()" builtin function).
> 
>   This approach would work well with counting mode PMCs
>   (both process and system-mode counting PMCs) and would
>   allow PMCs to be read at arbitrary points of time.
> 
>   We'll need a way of allocating system-wide & process-mode
>   PMCs; this could be done in userland (in dtrace(8)).
> 
> - hwpmc(4) can be augmented to be a 'DTrace provider'
>   allowing D scripts to be run, say when a PC sample is
>   recorded.

Before modifying the virtual machine in FreeBSD's DTrace port, it would
be best to discuss this in the "DTrace Community"
<http://www.opensolaris.org/jive/forum.jspa?forumID=7>

The Sun guys will guide us on which way they think is appropriate.

--
John Birrell