From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755969AbeASRTt (ORCPT ); Fri, 19 Jan 2018 12:19:49 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:53533 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932483AbeASRTe (ORCPT ); Fri, 19 Jan 2018 12:19:34 -0500 Date: Fri, 19 Jan 2018 18:19:29 +0100 From: Peter Zijlstra To: "Liang, Kan" Cc: "tglx@linutronix.de" , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , "acme@kernel.org" , "eranian@google.com" , "ak@linux.intel.com" Subject: Re: [PATCH V5 4/8] perf/x86/intel/uncore: add new data structures for free running counters Message-ID: <20180119171929.GZ2228@hirez.programming.kicks-ass.net> References: <1516042629-387021-1-git-send-email-kan.liang@intel.com> <1516042629-387021-4-git-send-email-kan.liang@intel.com> <20180118133248.GC2249@hirez.programming.kicks-ass.net> <37D7C6CF3E00A74B8858931C1DB2F07753801FEF@SHSMSX103.ccr.corp.intel.com> <20180119130731.GQ2228@hirez.programming.kicks-ass.net> <37D7C6CF3E00A74B8858931C1DB2F077538025E7@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077538025E7@SHSMSX103.ccr.corp.intel.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 19, 2018 at 03:15:00PM +0000, Liang, Kan wrote: > > > > On Thu, Jan 18, 2018 at 05:43:10PM +0000, Liang, Kan wrote: > > > In the uncore document, there is no event-code assigned to free running > > counters. > > > Some events need to be defined to indicate the free running counters. > > > The events are encoded as event-code + umask-code. > > > > > > The event-code for all free running counters is 0xff, which is the > > > same as the fixed counters. > > > > Is it possible to count the same things using the generic counters? > > > > Yes, there are events for generic counters to count bandwidth and > utilization. > > The reasons of introducing free running counters are > - To provide highly valuable information (bandwidth and utilization) > which most of the customers are interested in > - To save on the precious generic counters _IF_ the exact same counters are available on the GPs then we must use the same event code for them and use event scheduling to place them on fixed/free-running counters when possible. That's what we do for the CPU PMU's fixed counters too. Don't invent magic event codes just because.