Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031197Ab2EROKE (ORCPT ); Fri, 18 May 2012 10:10:04 -0400 Received: from s15943758.onlinehome-server.info ([217.160.130.188]:39810 "EHLO mail.x86-64.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933560Ab2EROKD (ORCPT ); Fri, 18 May 2012 10:10:03 -0400 Date: Fri, 18 May 2012 16:09:45 +0200 From: Borislav Petkov To: Peter Zijlstra Cc: Ingo Molnar , Frederic Weisbecker , Ingo Molnar , Steven Rostedt , LKML , Borislav Petkov Subject: Re: [PATCH 1/2] perf: Add persistent event facilities Message-ID: <20120518140945.GN20215@aftab.osrc.amd.com> References: <1332340496-21658-1-git-send-email-bp@amd64.org> <1332340496-21658-2-git-send-email-bp@amd64.org> <1337336040.573.12.camel@twins> <20120518110357.GH20215@aftab.osrc.amd.com> <1337340263.573.31.camel@twins> <20120518115957.GB19785@gmail.com> <20120518125505.GK20215@aftab.osrc.amd.com> <1337348267.573.37.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1337348267.573.37.camel@twins> 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: 1257 Lines: 38 On Fri, May 18, 2012 at 03:37:47PM +0200, Peter Zijlstra wrote: > On Fri, 2012-05-18 at 14:55 +0200, Borislav Petkov wrote: > > It is an interesting question how we handle that RO/RW thing? > > RO buffers overwrite, RW buffers loose events. > > We could allow both for persistent under the constraints: > > VM_SHARED - must imply !VM_WRITE since multiple people writing to the > control page will get 'interesting' very fast. Ok, I get that one. > !VM_SHARED - must fail mmap() of the debugfs file if there's already > an existing user. What happens here if a second user wants to enable a second set of persistent events, allocate a second set of per-CPU buffers? > Note that even RW buffers only allows writes to the control page, a > write to the actual data itself will generate a fault. Ok. -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 -- 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/