Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755447Ab3I3QQJ (ORCPT ); Mon, 30 Sep 2013 12:16:09 -0400 Received: from merlin.infradead.org ([205.233.59.134]:46029 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754790Ab3I3QQG (ORCPT ); Mon, 30 Sep 2013 12:16:06 -0400 Date: Mon, 30 Sep 2013 18:15:46 +0200 From: Peter Zijlstra To: Stephane Eranian Cc: LKML , "mingo@elte.hu" , "ak@linux.intel.com" , Arnaldo Carvalho de Melo , David Ahern , Jiri Olsa , Hugh Dickins Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions Message-ID: <20130930161546.GG3081@twins.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 1469 Lines: 31 On Mon, Sep 30, 2013 at 05:44:41PM +0200, Stephane Eranian wrote: > Hi, > > I was alerted by people trying to use the PERF_RECORD_MMAP2 > record to disambiguate virtual address mappings that there is a case > where the record does not contain enough information. > > As you know, the MMAP2 record adds the major, minor, ino number, > inode generation numbers to a mapping. But it does that only for > file or pseudo -file backed mappings. That covers file mmaps and also > SYSV shared memory segments. > > However there is a another kind of situation that arises in some > multi-process benchmarks where a region of memory is cloned > using VM_CLONE. As such, the virtual addresses match between > the processes but the major, minor, inode, inode generation fields > are all zeroes because there is no inode associated with the mapping. > Yet, it is important for the tool to know the mappings between the > processes are pointing to the same physical data. > > We need to cover this case and I am seeking for advice on how to > best address this need given that we discarded using the plain physical > address for disambiguation. Urgh.. who in his bloody mind is playing VM_CLNOE games that is not pthread_creatE() ? -- 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/