Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757019Ab3JIJ7M (ORCPT ); Wed, 9 Oct 2013 05:59:12 -0400 Received: from mail-ee0-f54.google.com ([74.125.83.54]:42128 "EHLO mail-ee0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811Ab3JIJ7K (ORCPT ); Wed, 9 Oct 2013 05:59:10 -0400 Date: Wed, 9 Oct 2013 11:59:06 +0200 From: Ingo Molnar To: Stephane Eranian Cc: David Ahern , LKML , Peter Zijlstra , "mingo@elte.hu" , "ak@linux.intel.com" , Arnaldo Carvalho de Melo , Jiri Olsa , Hugh Dickins Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions Message-ID: <20131009095906.GB17480@gmail.com> References: <52541556.5060907@gmail.com> <20131008194129.GC7315@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 1303 Lines: 34 * Stephane Eranian wrote: > > Instead of a full revert we could just turn off the ABI portion > > minimally and not recognize it for now. Assuming a more complete > > solution is in the works for v3.13. > > That's a possibility. They are also pieces in the perf tool itself. We > could certainly make the attr->mmap2 bit disappear. > > I think it boils down to how can we uniquely identify virtual mapping to > the same physical data either via shmat(), files, VM_CLONE. We had all > covered but the last case with the ino approach. We don't have a > solution for VM_CLONE yet. PeterZ didn't like exposing the physical RAM address, right? Peter: could we expose the page frame number instead? (Maybe mix it with a random seed through the hash-mixer and expose that.) User-space will thus be able to discover whether two pages are shared or not, but not extract other information. The global MM ID thing looked rather ugly as well. That way we could drop the inode info as well? That feels a bit hacky too. 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/