Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757414AbZCYQer (ORCPT ); Wed, 25 Mar 2009 12:34:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751907AbZCYQeg (ORCPT ); Wed, 25 Mar 2009 12:34:36 -0400 Received: from tx2ehsobe002.messaging.microsoft.com ([65.55.88.12]:48948 "EHLO TX2EHSOBE004.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750940AbZCYQef (ORCPT ); Wed, 25 Mar 2009 12:34:35 -0400 X-BigFish: VPS-25(zz1432R98dR1805Mzz1202hzzz2fh6bh65h) X-Spam-TCS-SCL: 4:0 Message-ID: <49CA5CFF.8090908@am.sony.com> Date: Wed, 25 Mar 2009 09:34:07 -0700 From: Tim Bird User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Russell King - ARM Linux CC: Frederic Weisbecker , Abhishek Sagar , linux-arm-kernel , linux kernel , Steven Rostedt , Ingo Molnar , =?UTF-8?B?VXdlIEtsZWluZS1Lw7ZuaWc=?= Subject: Re: Anyone working on ftrace function graph support on ARM? References: <49C936CA.8070800@am.sony.com> <20090324213618.GC5975@nowhere> <49C95EAF.7030901@gmail.com> <20090324224857.GE5975@nowhere> <20090325084248.GF4697@n2100.arm.linux.org.uk> In-Reply-To: <20090325084248.GF4697@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 25 Mar 2009 16:34:09.0450 (UTC) FILETIME=[85C840A0:01C9AD67] X-SEL-encryption-scan: scanned Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1212 Lines: 31 Russell King - ARM Linux wrote: > As pointed out in my previous mail, identifying where on the stack the > return address is stored is only possible for OABI with frame pointers. > > EABI will probably be possible with the stack unwinding code, but it > probably won't be cheap. The EABI unwinder is scheduled for merging > during the present now-open merge window. > -finstrument-functions is looking better and better. I know it adds more overhead than the mcount call, and may wreak havoc with the dynamic ftrace mechanisms, but at least the callouts are simple, clear, and you get both entry and exit, at fixed costs. I'll take a look at the EABI unwinder to see what kind of variability it introduces (e.g. if it does a stack scan or something). Thanks very much for the information! -- Tim ============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America ============================= -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/