From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752023Ab3FZPT5 (ORCPT ); Wed, 26 Jun 2013 11:19:57 -0400 Received: from merlin.infradead.org ([205.233.59.134]:60493 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368Ab3FZPT4 (ORCPT ); Wed, 26 Jun 2013 11:19:56 -0400 Date: Wed, 26 Jun 2013 12:33:03 +0200 From: Peter Zijlstra To: Ingo Molnar 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: <20130626103303.GB28407@twins.programming.kicks-ass.net> References: <1371824448-7306-1-git-send-email-eranian@google.com> <20130624084338.GI28407@twins.programming.kicks-ass.net> <20130625104700.GZ28407@twins.programming.kicks-ass.net> <20130625105123.GA13649@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130625105123.GA13649@gmail.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 25, 2013 at 12:51:23PM +0200, Ingo Molnar wrote: > 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. Its more difficult than that though :/ Suppose not all mmap events fit in the output buffer and you're not able to read from the buffer because you're stuck in the ioctl(). This means we need to either force userspace to use threads to reliably use the feature; or complicate the ioctl() to allow vma ranges -- which introduces an inherent race window etc.. Neither option are really pretty and we already have the maps parse code -- also its not _that_ hard to parse either.