From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757255AbZCOTWV (ORCPT ); Sun, 15 Mar 2009 15:22:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752997AbZCOTWL (ORCPT ); Sun, 15 Mar 2009 15:22:11 -0400 Received: from tomts20.bellnexxia.net ([209.226.175.74]:53437 "EHLO tomts20-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbZCOTWK (ORCPT ); Sun, 15 Mar 2009 15:22:10 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AtMEAFzsvElMQW1W/2dsb2JhbACBTs42g38G Date: Sun, 15 Mar 2009 15:22:05 -0400 From: Mathieu Desnoyers To: Ingo Molnar Cc: Frederic Weisbecker , LKML , Lai Jiangshan , Steven Rostedt , Peter Zijlstra , Jiaying Zhang , Martin Bligh Subject: Re: [RFC][PATCH 2/2] tracing/x86: basic implementation of syscall tracing for x86-64 Message-ID: <20090315192205.GA10131@Krystal> References: <1236401580-5758-1-git-send-email-fweisbec@gmail.com> <1236401580-5758-3-git-send-email-fweisbec@gmail.com> <20090313163207.GA3354@Krystal> <20090313163702.GA9082@elte.hu> <20090313165020.GD3354@Krystal> <20090315044405.GB11150@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20090315044405.GB11150@elte.hu> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 15:19:59 up 15 days, 15:46, 2 users, load average: 0.82, 0.59, 0.46 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar (mingo@elte.hu) wrote: > > * Mathieu Desnoyers wrote: > > > * Ingo Molnar (mingo@elte.hu) wrote: > > > > > > * Mathieu Desnoyers wrote: > > > > > > > * Frederic Weisbecker (fweisbec@gmail.com) wrote: > > > > > > > > > Provide the ptrace hooks and arch specific syscall numbers > > > > > to ftrace arch indepedant syscall numbers. For now it only > > > > > supports 4 syscalls to provide an example. > > > > > > > > > > > > > Hi Frederic, > > > > > > > > I already have the equivalent TIF_KERNEL_TRACE flag in my > > > > LTTng tree added to every Linux architecture. You might want > > > > to re-use this work rather than re-doing this. I don't mind > > > > changing the flag name. > > > > > > Yeah. Note that the TIF bits are just one part - there are other > > > bits needed for HAVE_FTRACE_SYSCALLS arch support. > > > > > > Also, i'd eventually expect the TIF bits to be converted to a > > > tracehook callback, not spread it to other architectures. > > > > > > > The nice part about the TIF bit is that it permits adding this > > syscall tracing feature without increasing the size of the > > thread_info struct nor adding any extra tests in entry.S. Does > > the tracehook callback have these features ? > > yes. Tracehook just factors out common interfacing points - with > one specific implementation for now: ptrace. For syscall tracing > that means it wraps TIF_SYSCALL_TRACE in essence. > > Ingo What overhead and latency does tracehooks add when - they are being enabled/disabled - once they are enabled ? Do they require to stop each and every thread upon activation ? I'll post my lttng trace flags for RFC, as it could save Frederic some duplicated work. Feel free to comment. Thanks, Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68