From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932463Ab0EKK3Z (ORCPT ); Tue, 11 May 2010 06:29:25 -0400 Received: from mga09.intel.com ([134.134.136.24]:56785 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932108Ab0EKK3Y (ORCPT ); Tue, 11 May 2010 06:29:24 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.53,206,1272870000"; d="scan'208";a="620667836" Subject: Re: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs From: Lin Ming To: Ingo Molnar Cc: Peter Zijlstra , Corey Ashford , Frederic Weisbecker , "eranian@gmail.com" , "Gary.Mohr@Bull.com" , "arjan@linux.intel.com" , "Zhang, Yanmin" , Paul Mackerras , "David S. Miller" , Russell King , Paul Mundt , lkml , Arnaldo Carvalho de Melo , Will Deacon , Maynard Johnson , Carl Love In-Reply-To: <20100511093151.GA24284@elte.hu> References: <20100510115344.GA11238@elte.hu> <4BE8931C.9070106@linux.vnet.ibm.com> <1273560419.5605.3426.camel@twins> <20100511072127.GB10421@elte.hu> <1273566031.30322.31.camel@minggr.sh.intel.com> <1273567815.5605.3491.camel@twins> <1273568620.30322.42.camel@minggr.sh.intel.com> <1273569154.5605.3499.camel@twins> <20100511091833.GB18869@elte.hu> <1273569877.5605.3509.camel@twins> <20100511093151.GA24284@elte.hu> Content-Type: text/plain Date: Tue, 11 May 2010 18:28:42 +0800 Message-Id: <1273573722.30322.73.camel@minggr.sh.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 (2.24.1-2.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2010-05-11 at 17:31 +0800, Ingo Molnar wrote: > * Peter Zijlstra wrote: > > > On Tue, 2010-05-11 at 11:18 +0200, Ingo Molnar wrote: > > > * Peter Zijlstra wrote: > > > > > > > The new PMUs will use a dynamic range that starts at PERF_TYPE_MAX. > > > > > > I dont think we should use a dynamic range of event sources - it's a > > > completely useless indirection that has no meaning to humans. > > > > > > As far as machine interfaces go a much cleaner approach would be to allow an > > > open fd to a sysfs file to be passed to sys_perf_event_open() - this would > > > identify the event source. This needs a small extension of the ABI but we > > > could thus get rid of the 'type' enumeration altogether and express _all_ > > > event sources via fds to sysfs files. > > > > Whatever, that's almost identical. [...] > > It's not identical: as we dont expose our mapping structure externally and > dont have to have some dynamic type ID allocation layer/mechanism. Also, using > fds is an elegant, Linuxish way of expressing some object's identity and > passing it along. Don't understand this well enough. Does it need to attach pmu info to the sys file? For example, Does "perf top -e cycles" work as below? 1. get the pmu file of cycles events, ie, /sys/devices/system/cpu/cpu_hw_events/event_source_id 2. fd = open("/sys/devices/system/cpu/cpu_hw_events/event_source_id") 3. perf_event_attr::type = fd | (1<<31) 4. In kernel, perf_event_lookup_pmu() finds pmu by fd -> sys file -> pmu > > ( It also removes the possibility to intentionally or accidentally have type > IDs that are not reachable via the sysfs and vica verse. ) > > > [...] What we can do is reserve perf_event_attr::type with bit 31 set for > > fd's and use the fd->file lookup instead of the type->pmu lookup. > > Yeah, that sounds good. > > Ingo