From owner-freebsd-arch@FreeBSD.ORG Thu Dec 27 04:21:56 2012 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 131B9544 for ; Thu, 27 Dec 2012 04:21:56 +0000 (UTC) (envelope-from peter@wemm.org) Received: from mail-vb0-f50.google.com (mail-vb0-f50.google.com [209.85.212.50]) by mx1.freebsd.org (Postfix) with ESMTP id A8A2D8FC0A for ; Thu, 27 Dec 2012 04:21:55 +0000 (UTC) Received: by mail-vb0-f50.google.com with SMTP id fr13so9483058vbb.9 for ; Wed, 26 Dec 2012 20:21:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wemm.org; s=google; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=KKLPa+rkzvCfjcHmMGOIJym+4FCcYJoAGbBSDQDV358=; b=Y5dOhUvTKAOqm1qeJlPktt/cOjnDY1icVZLtpbKHU5wLKzvOECp/nXOw5FWyoOSVcG A26i2CAvfH+WHZBjGW01KpU1gi0GyoX0D+oUnPcn+NwPs1fvZlNtF+7L+N9DptN3jDc2 G3ghmpweKqUe31AEjJcIhEhiTriyaccUDZ+l4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:x-gm-message-state; bh=KKLPa+rkzvCfjcHmMGOIJym+4FCcYJoAGbBSDQDV358=; b=iZhmXGLZGYEafLXB9Qs0d3doCjjhtfFnT2ttuvFTs9Ds4rBpMxeQTXd4KryHrKZfPQ 2ne+hSNFTM1fcrKee3JmlNpuE1xaE/VIwVMJvRaqxZNI6muAxyGxuIceTpydZzLUe3GG 3hqL7V8417AeE6+06hJDbnI2dh8j9dDXjIR4/8VdCIUqL4uyf/WccUAK3aE7qO4fmdx0 8GXXjiH+VJs21iBfxnIJoC419ijTNMr8ZlMqhzUcQEn/+zfNKX6gGEAM6jbEvgRnXl4D 0Jx7W+4lMpt8tfeYs3kpAGMP7QytXJ5W8OShiy3/6uxnRF5ifmudvEkM8Wp8TOqEiv81 slNw== MIME-Version: 1.0 Received: by 10.52.27.138 with SMTP id t10mr40027392vdg.81.1356582114710; Wed, 26 Dec 2012 20:21:54 -0800 (PST) Received: by 10.220.205.6 with HTTP; Wed, 26 Dec 2012 20:21:54 -0800 (PST) In-Reply-To: <50DBC7E2.1070505@mu.org> References: <50D49DFF.3060803@ixsystems.com> <50DBC7E2.1070505@mu.org> Date: Wed, 26 Dec 2012 20:21:54 -0800 Message-ID: Subject: Re: UPDATE Re: making use of userland dtrace on FreeBSD From: Peter Wemm To: Alfred Perlstein Content-Type: text/plain; charset=ISO-8859-1 X-Gm-Message-State: ALoCoQkyiGbMAcELkXtnYeP9rRGsA2r0+15ELlimoEalWxOEBy8TXpg3xqHyvDUsFGYzHtP1+5CN Cc: "arch@freebsd.org" , Adrian Chadd , Rui Paulo , Alfred Perlstein X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Dec 2012 04:21:56 -0000 On Wed, Dec 26, 2012 at 8:00 PM, Alfred Perlstein wrote: > What would be the drawbacks? I don't want to hurt freebsd for heavy > performance, but I think this functionality should work out of the box for > most people. The drawbacks are mostly performance related. It defeats a certain hardware optimizations for call/return on leaf functions. It'll mostly affect things like math, crypto, compression and multimedia libraries (that's ffmpeg, bzip2/gzip/libarchive, openssl, etc) but, we generally don't seem to care about that sort of performance anyway, so what's one more loss? Of course it wouldn't be required with dwarf unwinding awareness, but we don't have that. We have -fno-omit-frame-pointer on the amd64 kernel whenever debugging is compiled in because there's no unwinder for doing stack traces. We need a dwarf2+ unwinder and somebody to instrument the call frame state through the remaining assembler code. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV "All of this is for nothing if we don't go to the stars" - JMS/B5 "If Java had true garbage collection, most programs would delete themselves upon execution." -- Robert Sewell bitcoin:188ZjyYLFJiEheQZw4UtU27e2FMLmuRBUE