From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10906 invoked by alias); 27 Nov 2012 14:26:50 -0000 Received: (qmail 10889 invoked by uid 22791); 27 Nov 2012 14:26:48 -0000 X-SWARE-Spam-Status: No, hits=-7.7 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,RCVD_IN_DNSWL_HI,RCVD_IN_HOSTKARMA_W,RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mga11.intel.com (HELO mga11.intel.com) (192.55.52.93) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 27 Nov 2012 14:26:39 +0000 Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP; 27 Nov 2012 06:26:38 -0800 X-ExtLoop1: 1 Received: from irsmsx104.ger.corp.intel.com ([163.33.3.159]) by fmsmga001.fm.intel.com with ESMTP; 27 Nov 2012 06:26:36 -0800 Received: from irsmsx102.ger.corp.intel.com ([169.254.2.95]) by IRSMSX104.ger.corp.intel.com ([169.254.5.151]) with mapi id 14.01.0355.002; Tue, 27 Nov 2012 14:25:39 +0000 From: "Metzger, Markus T" To: Jan Kratochvil CC: "gdb-patches@sourceware.org" , "markus.t.metzger@gmail.com" , "palves@redhat.com" , "tromey@redhat.com" , "kettenis@gnu.org" Subject: RE: [patch v4 00/13] branch tracing support for Atom Date: Tue, 27 Nov 2012 14:26:00 -0000 Message-ID: References: <1354013351-14791-1-git-send-email-markus.t.metzger@intel.com> <20121127131055.GB22431@host2.jankratochvil.net> In-Reply-To: <20121127131055.GB22431@host2.jankratochvil.net> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2012-11/txt/msg00734.txt.bz2 > -----Original Message----- > From: gdb-patches-owner@sourceware.org [mailto:gdb-patches-owner@sourcewa= re.org] On Behalf Of Jan Kratochvil > Sent: Tuesday, November 27, 2012 2:11 PM > To: Metzger, Markus T > Cc: gdb-patches@sourceware.org; markus.t.metzger@gmail.com; palves@redhat= .com; tromey@redhat.com; kettenis@gnu.org > Subject: Re: [patch v4 00/13] branch tracing support for Atom > Importance: High >=20 > On Tue, 27 Nov 2012 11:48:58 +0100, markus.t.metzger@intel.com wrote: > > - "btrace list" prints the blocks that have been traced; one line per= block. > [...] > > - "btrace" prints the branch trace disassembly >=20 > I see a partially similar reverse execution feature for GDB I use. >=20 > There one can easily find the interesting spot using the back-and-forth m= oving > in the history using reverse-next, reverse-step, reverse-finish, but even > finding back the spot by regular step/next/finish (only stepping in histo= ry). >=20 > But with reverse execution one (I) commonly use also watchpoints to find = the > spot, which is apparently not applicable with btrace. Also the natural > "backtrace" command would not work with btrace. While the most correct w= ay > would be to make all memory as in practice one may want to = print > variables when stepping in the btrace history so there could be an except= ion > for "print" command to temporarily make memory available with a warning. > Just such an idea. >=20 > Reverse execution does not have such feature of the "listing" of its hist= ory. > So unifying their interface could provide both "reverse-*" commands > functionality with btrace and "listing" of the reverse-execution history. >=20 > Being used to reverse execution I find more natural to "reverse-step" to = look > where the inferior was before a moment. >=20 > But not sure if unifying btrace with reverse execution is a good idea at = all > having no practical experience with btrace yet. Hmmm, I never thought about using the reverse execution cli for btrace. Thi= s might give the impression that btrace were more powerful than it actually= is. I see btrace as a lower-cost alternative to reverse execution. It is l= ess powerful but faster. I would also expect problems with stepping, since we won't be able to fake = a back trace using branch trace data. I don't expect that commands like rev= erse-next, next, and finish would work without special cases for btrace. Regarding the btrace list feature, this might be something we may want to a= dd to reverse execution. It gives an overview over the executed code in a v= ery compact format. If people find this useful, we could compute something = similar from the reverse execution history. Regards, Markus. Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen, Deutschland Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Peter Gleissner, Christian Lamprechter, Hannes Schwadere= r, Douglas Lusk Registergericht: Muenchen HRB 47456 Ust.-IdNr./VAT Registration No.: DE129385895 Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052