From owner-freebsd-arch@FreeBSD.ORG Sun Jan 21 23:30:42 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 788DE16A403 for ; Sun, 21 Jan 2007 23:30:42 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from nf-out-0910.google.com (nf-out-0910.google.com [64.233.182.191]) by mx1.freebsd.org (Postfix) with ESMTP id 1109313C44B for ; Sun, 21 Jan 2007 23:30:41 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: by nf-out-0910.google.com with SMTP id m19so315824nfc for ; Sun, 21 Jan 2007 15:30:40 -0800 (PST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=Fl6uE/VomJWuS2kTs9JrdCLa+AscEnZQw3mjGkAV2zibQrCMOZIZSE7VdlsAHDuqRS0i7xRCRhJ8QbXH9C8urG/eF0Cu4TchUXm+pHnCcDT2dMak7Un553k8UVKj8Jlanmyjw8antu93OPg4uQ3da0507HsDcSuiuvyQxyAKHrc= Received: by 10.48.48.13 with SMTP id v13mr91419nfv.1169422240526; Sun, 21 Jan 2007 15:30:40 -0800 (PST) Received: by 10.48.238.14 with HTTP; Sun, 21 Jan 2007 15:30:40 -0800 (PST) Message-ID: <3bbf2fe10701211530o7c2e8977k2df02a546cb4cb8f@mail.gmail.com> Date: Mon, 22 Jan 2007 00:30:40 +0100 From: "Attilio Rao" Sender: asmrookie@gmail.com To: "Luigi Rizzo" In-Reply-To: <20070121152251.A84413@xorpc.icir.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20070121140019.A83688@xorpc.icir.org> <20070121152251.A84413@xorpc.icir.org> X-Google-Sender-Auth: b8a6dbd2e12ceeb1 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 23:30:42 -0000 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). Attilio -- Peace can only be achieved by understanding - A. Einstein