From owner-freebsd-current@FreeBSD.ORG Tue Nov 25 00:17:57 2003 Return-Path: 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 1211F16A4CE for ; Tue, 25 Nov 2003 00:17:57 -0800 (PST) Received: from harmony.village.org (rover.bsdimp.com [204.144.255.66]) by mx1.FreeBSD.org (Postfix) with ESMTP id E120643FE3 for ; Tue, 25 Nov 2003 00:17:55 -0800 (PST) (envelope-from imp@bsdimp.com) Received: from localhost (warner@rover2.village.org [10.0.0.1]) by harmony.village.org (8.12.9p2/8.12.9) with ESMTP id hAP8Hrlg032128; Tue, 25 Nov 2003 01:17:53 -0700 (MST) (envelope-from imp@bsdimp.com) Date: Tue, 25 Nov 2003 01:17:34 -0700 (MST) Message-Id: <20031125.011734.118629079.imp@bsdimp.com> To: peterjeremy@optushome.com.au From: "M. Warner Losh" In-Reply-To: <20031125080155.GC76478@server.vk2pj.dyndns.org> References: <200311242125.13786.sam@errno.com> <20031124.231607.128865107.imp@bsdimp.com> <20031125080155.GC76478@server.vk2pj.dyndns.org> X-Mailer: Mew version 2.1 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit cc: freebsd-current@freebsd.org cc: gallatin@cs.duke.edu Subject: Re: 40% slowdown with dynamic /bin/sh X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Nov 2003 08:17:57 -0000 X-List-Received-Date: Tue, 25 Nov 2003 08:17:57 -0000 In message: <20031125080155.GC76478@server.vk2pj.dyndns.org> Peter Jeremy writes: : On Mon, Nov 24, 2003 at 11:16:07PM -0700, M. Warner Losh wrote: : >Hmmmm, It looks like the hit is less than 10% in the fork intensive : >test I just wrote: : > : >#!/bin/sh : >for i in 0 1 2 3 4 5 6 7 8 9; do : > for j in 0 1 2 3 4 5 6 7 8 9; do : > for k in 0 1 2 3 4 5 6 7 8 9; do : > for l in 0 1 2 3 4 5 6 7 8 9; do : > for m in 0 1 2 3 4 5 6 7 8 9; do : > for n in 0 1 2 3 4 5 6 7 8 9; do : > true; : >done; done; done; done; done; done; : : Unless you've done something wierd to your /bin/sh, "true" is a : builtin. This test just to measures the ongoing runtime overhead : of a dynamic executable (ie PIC code). Drew's test was measuring : the startup overhead. True. However, I get very similar numbers of I change it to /usr/bin/true (12% slower). /bin/sh usually fork+exec things other /bin/sh. : >Clearly dynamic is slower, but it is more like 11% slower (10.67%) on : >the average than 40% slower. I think this would be a more typical : >usage pattern. : : You have measured different things. Drew's test shows that a dynamic : /bin/sh tahes about 40% longer to start. Your test shows that once : started, it runs about 11% slower. And the 11% slower is _very_ : worrying since it is probably more widely applicable than just /bin/sh. Dynamically linked prorgrams tend to be a few percent slower than their static counterparts due to PIC code typically being slower than non-PIC code. There's nothing new here. Clearly there are problems to look into, but it isn't the end of the world. Warner