Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759234AbZFJNX7 (ORCPT ); Wed, 10 Jun 2009 09:23:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755749AbZFJNXv (ORCPT ); Wed, 10 Jun 2009 09:23:51 -0400 Received: from mga02.intel.com ([134.134.136.20]:55962 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753173AbZFJNXv convert rfc822-to-8bit (ORCPT ); Wed, 10 Jun 2009 09:23:51 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.41,341,1241420400"; d="scan'208";a="420485019" From: "Metzger, Markus T" To: Ingo Molnar , Peter Zijlstra CC: "mingo@redhat.com" , "hpa@zytor.com" , "linux-kernel@vger.kernel.org" , "tglx@linutronix.de" , "oleg@redhat.com" , "linux-tip-commits@vger.kernel.org" Date: Wed, 10 Jun 2009 14:22:40 +0100 Subject: RE: [tip:tracing/core] x86, bts: reenable ptrace branch trace support Thread-Topic: [tip:tracing/core] x86, bts: reenable ptrace branch trace support Thread-Index: Acnpyiap/omPA/1VRNWDsVXyrlv40gAArXOg Message-ID: <928CFBE8E7CB0040959E56B4EA41A77EBBC651E2@irsmsx504.ger.corp.intel.com> References: <20090424094448.A30216@sedona.ch.intel.com> <1244637843.13761.11786.camel@twins> <20090610125108.GA13506@elte.hu> In-Reply-To: <20090610125108.GA13506@elte.hu> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3397 Lines: 86 >-----Original Message----- >From: Ingo Molnar [mailto:mingo@elte.hu] >Sent: Wednesday, June 10, 2009 2:51 PM >To: Peter Zijlstra >Cc: mingo@redhat.com; hpa@zytor.com; linux-kernel@vger.kernel.org; Metzger, Markus T; >tglx@linutronix.de; oleg@redhat.com; linux-tip-commits@vger.kernel.org >Subject: Re: [tip:tracing/core] x86, bts: reenable ptrace branch trace support > > >* Peter Zijlstra wrote: > >> On Thu, 2009-05-07 at 09:25 +0000, tip-bot for Markus Metzger wrote: >> > Commit-ID: 7e0bfad24d85de7cf2202a7b0ce51de11a077b21 >> > Gitweb: http://git.kernel.org/tip/7e0bfad24d85de7cf2202a7b0ce51de11a077b21 >> > Author: Markus Metzger >> > AuthorDate: Fri, 24 Apr 2009 09:44:48 +0200 >> > Committer: Ingo Molnar >> > CommitDate: Fri, 24 Apr 2009 10:18:51 +0200 >> > >> > x86, bts: reenable ptrace branch trace support >> > >> > The races found by Oleg Nesterov have been fixed. >> > >> > Reenable branch trace support. >> > >> > Signed-off-by: Markus Metzger >> > Acked-by: Oleg Nesterov >> > LKML-Reference: <20090424094448.A30216@sedona.ch.intel.com> >> > Signed-off-by: Ingo Molnar >> >> OK, this whole BTS thing worries me because it seems to expose too >> much of the Intel Debug Store thingy to the outside world. >> >> The thing is, once we do PEBS from inside the kernel, we'll have >> to share the debug store, and the way this thing sets it up isn't >> really going to work. >> >> So what I'd like to see is having this debug store removed from >> the interface and abstracted away as cpu resource -- a single page >> when in use should suffice I think. >> >> If you want to expose a buffer to userspace, use the regular >> mmap() interface and fill those pages from the DS interrupt >> handler. > >hm, that makes sense indeed. We are in the merge window now - >Markus, what's your suggestion? The Debug Store interface is completely in-kernel. It does not expose anything to the outside world. What we expose is a ptrace interface for branch tracing. That this is built on top of Debug Store is completely hidden. The Debug Store interface may be changed without impacting the user-visible part at any time. I do think that a ptrace interface makes sense since debuggers are the targeted users for branch tracing. I don't see why we should not merge the fixes now and then rework the in-kernel parts as needed for supporting PEBS. regards, markus. --------------------------------------------------------------------- Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen Germany Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer Registergericht: Muenchen HRB 47456 Ust.-IdNr. VAT Registration No.: DE129385895 Citibank Frankfurt (BLZ 502 109 00) 600119052 This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. -- 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/