From owner-freebsd-arch@FreeBSD.ORG Sun Jan 21 23:49:04 2007 Return-Path: X-Original-To: freebsd-arch@freebsd.org Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 201C216A401; Sun, 21 Jan 2007 23:49:04 +0000 (UTC) (envelope-from rizzo@icir.org) Received: from xorpc.icir.org (xorpc.icir.org [192.150.187.68]) by mx1.freebsd.org (Postfix) with ESMTP id E3F7F13C448; Sun, 21 Jan 2007 23:49:03 +0000 (UTC) (envelope-from rizzo@icir.org) Received: from xorpc.icir.org (localhost [127.0.0.1]) by xorpc.icir.org (8.12.11/8.13.6) with ESMTP id l0LNn2Nj084710; Sun, 21 Jan 2007 15:49:02 -0800 (PST) (envelope-from rizzo@xorpc.icir.org) Received: (from rizzo@localhost) by xorpc.icir.org (8.12.11/8.12.3/Submit) id l0LNn1Bd084709; Sun, 21 Jan 2007 15:49:01 -0800 (PST) (envelope-from rizzo) Date: Sun, 21 Jan 2007 15:49:01 -0800 From: Luigi Rizzo To: Attilio Rao Message-ID: <20070121154901.B84480@xorpc.icir.org> References: <20070121140019.A83688@xorpc.icir.org> <20070121152251.A84413@xorpc.icir.org> <3bbf2fe10701211530o7c2e8977k2df02a546cb4cb8f@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <3bbf2fe10701211530o7c2e8977k2df02a546cb4cb8f@mail.gmail.com>; from attilio@freebsd.org on Mon, Jan 22, 2007 at 12:30:40AM +0100 Cc: Ivan Voras , freebsd-arch@freebsd.org Subject: Re: bzero & bcopy alignment X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Jan 2007 23:49:04 -0000 On Mon, Jan 22, 2007 at 12:30:40AM +0100, Attilio Rao wrote: > 2007/1/22, Luigi Rizzo : > > On Sun, Jan 21, 2007 at 11:25:14PM +0100, Ivan Voras wrote: > > > Luigi Rizzo wrote: > > > > On Sun, Jan 21, 2007 at 10:41:09PM +0100, Ivan Voras wrote: > > > >> Following recent discussion on alignment of bzero() and bcopy(), I've > > > >> added some statistics collecting code to bzero() and bcopy() for > > > >> practice (on a RELENG_6 box), and here are the cumulative results for > > > >> argument alignment: > > > > > > > > i think these profiles depend heavily on the hardware > > > > and usage patterns. > > > > > > Yes, I agree. For what it's worth, this was on vmware, almost no network > > > activity. > > > > > > > e.g. some network drivers force you to aligned buffers > > > > which results in misaligned payload requesting in > > > > turn an unaligned bcopy. Not that one can help with this, > > > > but i think that is also important to locate the locations > > > > in the source where the poorly aligned (1-2, maybe > > > > 4 and 8 to some degree) ops occur. > > > > > > Any magic tricks to identify the caller of "current" function in the kernel? > > > > i suppose i would remap those function as > > > > #define bcopy(a, b, c) \ > > do { \ > > track_bcopy(__PRETTY_FUNCTION__, __FILE__, __LINE__, a, b, c); > > original_bcopy(a, b, c); > > } > > > > and the same for bzero, and then use function track_bcopy() > > to simply record the instances in some data structure that you > > can then export in some way to userland for stats gathering. > > In the simplest form you could e.g. filter unaligned accesses > > and just dump them to a buffer exported via sysctl; > > if you want to make things smarter/more efficient, you could > > hash __FILE__, __LINE__ to avoid duplicates (and probably, > > because these are constant strings, you can just compare > > the string pointers without having to do a full strcmp). > > A better approach (at least for ia32, I'm not aware what is the > situation on the other architectures) would be using the vectorized > entry for this family of function (i386/include/md_var.h). you still need the macro wrappers to acquire __FILE__ and __LINE__ information. cheers luigi