Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752841Ab3FYKvc (ORCPT ); Tue, 25 Jun 2013 06:51:32 -0400 Received: from mail-ea0-f172.google.com ([209.85.215.172]:37800 "EHLO mail-ea0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752536Ab3FYKv2 (ORCPT ); Tue, 25 Jun 2013 06:51:28 -0400 Date: Tue, 25 Jun 2013 12:51:23 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Stephane Eranian , LKML , "mingo@elte.hu" , "ak@linux.intel.com" , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim Subject: Re: [PATCH 0/8] perf: add ability to sample physical data addresses Message-ID: <20130625105123.GA13649@gmail.com> References: <1371824448-7306-1-git-send-email-eranian@google.com> <20130624084338.GI28407@twins.programming.kicks-ass.net> <20130625104700.GZ28407@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130625104700.GZ28407@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1576 Lines: 42 * Peter Zijlstra wrote: > On Tue, Jun 25, 2013 at 11:59:09AM +0200, Stephane Eranian wrote: > > One guarantee we have is that the physical does correspond to the virtual > > address at the time of the interrupt. > > That might not be much of a guarantee depending on the circumstances. > > > But yeah, if physical pages are swapped during the run, then things become > > a lot more complicated. I am not trying to address this. > > > > Can page move for shared memory segments? > > Yep.. > > > > Such would completely shatter physical page relations. > > > > > > If the shared memory thing is really the issue, doesn't perf already > > > have the process memory layout (/proc/$PID/maps and aux stream mmap > > > updates) with which it can compute map relative offsets and compare > > > thusly? > > > > Not sure I understand this. > > suppose the same shared memory segment is mapped at two different > > addresses by shmat(). First, I don't know if those show up in /proc/maps. > > They should; IIRC maps is a full vma list.. /me prods about in > fs/proc/task_mmu.c.. yes it prints all vmas. A syscall (ioctl?) to dump all current vmas into the mmap update stream (to form a starting point) might be handy - that would remove the fragility and overhead of parsing /proc/ details. Thanks, Ingo -- 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/