From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754737AbXLMNIu (ORCPT ); Thu, 13 Dec 2007 08:08:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752256AbXLMNIm (ORCPT ); Thu, 13 Dec 2007 08:08:42 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:60536 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752041AbXLMNIl (ORCPT ); Thu, 13 Dec 2007 08:08:41 -0500 Date: Thu, 13 Dec 2007 14:08:14 +0100 From: Ingo Molnar To: "Metzger, Markus T" Cc: ak@suse.de, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, markus.t.metzger@gmail.com, "Siddha, Suresh B" , roland@redhat.com, akpm@linux-foundation.org, mtk.manpages@gmail.com, Alan Stern Subject: Re: x86, ptrace: support for branch trace store(BTS) Message-ID: <20071213130814.GC28340@elte.hu> References: <20071210123809.A14251@sedona.ch.intel.com> <20071210202052.GA26002@elte.hu> <029E5BE7F699594398CA44E3DDF5544401130A1E@swsmsx413.ger.corp.intel.com> <20071211145301.GA19427@elte.hu> <029E5BE7F699594398CA44E3DDF554440115D3C5@swsmsx413.ger.corp.intel.com> <20071212110330.GD1611@elte.hu> <029E5BE7F699594398CA44E3DDF554440115D6DC@swsmsx413.ger.corp.intel.com> <20071213102939.GS8977@elte.hu> <029E5BE7F699594398CA44E3DDF5544401186D54@swsmsx413.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <029E5BE7F699594398CA44E3DDF5544401186D54@swsmsx413.ger.corp.intel.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Metzger, Markus T wrote: > The ptrace API would allow the user to: > - define (and query) the overflow mechanism > (wrap-around or event) > - define (and query) the size of the buffer within certain limits > (we could either give an error or cut off) > - define (and query) events to be monitored > (last branch trace, scheduling timestamps) > - get a single BTS record > - query the number of BTS records > (to find out how big your drain buffer needs to be; it may be bigger > than you requested) > - drain all BTS records (copy, then clear) > - clear all BTS records > > Draining would require the user to allocate a buffer to hold the data, > which might not be feasible when he is near his memory limit. He could > fall back to looping over the single-entry get. It is questionable, > how useful the drain ptrace command would actually be; we might want > to replace it with a get range command. > > Are you OK with this? this sounds a lot more flexible to me. Please, once it looks good to all of us also extend LTP's ptrace bits with unit tests for these API additions. (Cc: such LTP bits to subrata@linux.vnet.ibm.com) Ingo