Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753505Ab0APPvL (ORCPT ); Sat, 16 Jan 2010 10:51:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753246Ab0APPvK (ORCPT ); Sat, 16 Jan 2010 10:51:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53593 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753168Ab0APPvG (ORCPT ); Sat, 16 Jan 2010 10:51:06 -0500 To: Jim Keniston Cc: Srikar Dronamraju , Peter Zijlstra , Arnaldo Carvalho de Melo , Frederic Weisbecker , LKML , Mark Wielaard , utrace-devel Subject: Re: [RFC] [PATCH 4/7] Uprobes Implementation References: <20100111122553.22050.46895.sendpatchset@srikar.in.ibm.com> <1263467394.4244.291.camel@laptop> <1263509380.4875.35.camel@localhost.localdomain> <1263546632.4244.352.camel@laptop> <1263548124.4244.358.camel@laptop> <20100115131037.GP4822@redhat.com> <1263561930.4244.417.camel@laptop> <20100115133825.GQ4822@redhat.com> <1263563276.4244.426.camel@laptop> <20100115142007.GA1628@linux.vnet.ibm.com> <1263597085.5007.82.camel@localhost.localdomain> From: fche@redhat.com (Frank Ch. Eigler) Date: Sat, 16 Jan 2010 10:50:48 -0500 In-Reply-To: <1263597085.5007.82.camel@localhost.localdomain> (Jim Keniston's message of "Fri, 15 Jan 2010 15:11:25 -0800") Message-ID: User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jim Keniston writes: > [...] > Years ago, we had pre-utrace versions of uprobes where the uprobes > breakpoint-handler code was dispatched from the die_notifier, before the > int3 turned into a SIGTRAP. I believe that's what Peter is > recommending. On my old Pentium M... > - a pre-utrace uprobe hit cost about 1 usec; > - a utrace-based uprobe hit cost about 3 usec; > [...] > So yeah, learning about the int3 via utrace after the SIGTRAP gets > created adds some overhead to uprobes. [...] Was this test comparing likewise fruit? For example, did it account for factors where other processes were gdb-int3-instrumented or with lots of kprobes active? Differently multithreaded? Demultiplexing probes amongst multiple processes? (It's counterintuitive that the utrace/kernel int3->sigtrap dispatching code alone should cause thousands of extra instructions.) - FChE -- 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/