From owner-freebsd-arch@FreeBSD.ORG Sat Apr 19 15:56:49 2008 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EAAB9106566B for ; Sat, 19 Apr 2008 15:56:49 +0000 (UTC) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (troutmask.apl.washington.edu [128.208.78.105]) by mx1.freebsd.org (Postfix) with ESMTP id C00F48FC16 for ; Sat, 19 Apr 2008 15:56:49 +0000 (UTC) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (localhost.apl.washington.edu [127.0.0.1]) by troutmask.apl.washington.edu (8.14.2/8.14.2) with ESMTP id m3JFtKZM055693; Sat, 19 Apr 2008 08:55:20 -0700 (PDT) (envelope-from sgk@troutmask.apl.washington.edu) Received: (from sgk@localhost) by troutmask.apl.washington.edu (8.14.2/8.14.2/Submit) id m3JFtJOp055692; Sat, 19 Apr 2008 08:55:19 -0700 (PDT) (envelope-from sgk) Date: Sat, 19 Apr 2008 08:55:19 -0700 From: Steve Kargl To: Jeremie Le Hen Message-ID: <20080419155519.GA55562@troutmask.apl.washington.edu> References: <20080418132749.GB4840@obiwan.tataz.chchile.org> <200804181945.59189.max@love2party.net> <20080418204738.GE4840@obiwan.tataz.chchile.org> <20080419001555.GA50009@troutmask.apl.washington.edu> <20080419074638.GH4840@obiwan.tataz.chchile.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080419074638.GH4840@obiwan.tataz.chchile.org> User-Agent: Mutt/1.4.2.3i Cc: freebsd-arch@freebsd.org Subject: Re: Integration of ProPolice in FreeBSD 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: Sat, 19 Apr 2008 15:56:50 -0000 On Sat, Apr 19, 2008 at 09:46:38AM +0200, Jeremie Le Hen wrote: > Hi Steve, > > On Fri, Apr 18, 2008 at 05:15:55PM -0700, Steve Kargl wrote: > > On Fri, Apr 18, 2008 at 10:47:38PM +0200, Jeremie Le Hen wrote: > > > > > > Certainly. I would like to hear opinion from other committers if SSP > > > should be enabled by default. > > > > I'm not a committer, but I'll ask a question anyway. > > > > Can you quantify the performance impact, in particular for > > numerically intensive codes with heavy use of libm? > > I don't run such application, so I can't answer. Sorry. If you are > willing to give a try, I would be pleased to help you to run your tests, > or even run them on my side. > > BTW for the sake of my curiosity, is there a technical reason for > ProPolice to be heavier for libm? > Most numerical applications, that I'm familiar with, tend to contain nested loops that make calls to functions in libm. Simple example in one of my codes is a 3 deep loop that computes what is known as the thermal dose. for (k = 0; k < kmax; k++) for (j = 0; j < jmax; j++) for (i = 0; i < imax; i++) td += exp(a * b[k][j][i]) Now, put the above loops inside a time loop with n time steps. exp() will be called kmax*jmax*imax*n times where this product can be quite large (order of 5e11). Any overhead caused by PP will increase the simulation time. A 1% increase in time is probably tolerable, but a 10% increase would be detrimental to simulations that takes days to complete (yes, I have a few that run that long). I'll see if I can get you some numbers this weekend. -- Steve