Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754139Ab0ARNHW (ORCPT ); Mon, 18 Jan 2010 08:07:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752102Ab0ARNHV (ORCPT ); Mon, 18 Jan 2010 08:07:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:9060 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751598Ab0ARNHU (ORCPT ); Mon, 18 Jan 2010 08:07:20 -0500 Message-ID: <4B545CE5.6090506@redhat.com> Date: Mon, 18 Jan 2010 15:06:45 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091209 Fedora/3.0-4.fc12 Thunderbird/3.0 MIME-Version: 1.0 To: Pekka Enberg CC: Srikar Dronamraju , Peter Zijlstra , ananth@in.ibm.com, Jim Keniston , Ingo Molnar , Arnaldo Carvalho de Melo , utrace-devel , Frederic Weisbecker , Masami Hiramatsu , Maneesh Soni , Mark Wielaard , LKML Subject: Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP) References: <1263740593.557.20967.camel@twins> <1263800752.4283.19.camel@laptop> <4B543F93.3060509@redhat.com> <1263815072.4283.305.camel@laptop> <4B544D7C.2060708@redhat.com> <1263816396.4283.361.camel@laptop> <4B544F8E.1080603@redhat.com> <84144f021001180413w76a8ca2axb0b9f07ee4dea67e@mail.gmail.com> <4B545146.3080001@redhat.com> <20100118124419.GC1628@linux.vnet.ibm.com> <84144f021001180451k2a84f17x3dc24796fea986c9@mail.gmail.com> <4B5459CA.9060603@redhat.com> <4B545ACF.40203@cs.helsinki.fi> In-Reply-To: <4B545ACF.40203@cs.helsinki.fi> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1523 Lines: 35 On 01/18/2010 02:57 PM, Pekka Enberg wrote: > On 01/18/2010 02:51 PM, Pekka Enberg wrote: >>> And how many probes do we expected to be live at the same time in >>> real-world scenarios? I guess Avi's "one million" is more than enough? > > Avi Kivity kirjoitti: >> I don't think a user will ever come close to a million, but we can >> expect some inflation from inlined functions (I don't know if uprobes >> replicates such probes, but if it doesn't, it should). > > Right. I guess we're looking at few megabytes of the address space for > normal scenarios which doesn't seem too excessive. > > However, as Peter pointed out, the bigger problem is that now we're > opening the door for other features to steal chunks of the address > space. And I think it's a legitimate worry that it's going to cause > problems for 32-bit in the future. > > I don't like the idea but if the performance benefits are real (are > they?), maybe it's a worthwhile trade-off. Dunno. If uprobes can trace to buffer memory in the process address space, I think the win can be dramatic. Incidentally it will require injecting even more vmas into a process. Basically it means very low cost tracing, like the kernel tracers. -- error compiling committee.c: too many arguments to function -- 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/