From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932609AbbJ0PqR (ORCPT ); Tue, 27 Oct 2015 11:46:17 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:55575 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932256AbbJ0PqP (ORCPT ); Tue, 27 Oct 2015 11:46:15 -0400 Message-ID: <562F9C44.50702@codeaurora.org> Date: Tue, 27 Oct 2015 11:46:12 -0400 From: Christopher Covington User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:36.0) Gecko/20100101 Thunderbird/36.0 MIME-Version: 1.0 To: Will Deacon , Drew Richardson CC: Russell King , Peter Zijlstra , "linux-kernel@vger.kernel.org" , Arnaldo Carvalho de Melo , Ingo Molnar , Wade Cherry , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] arm: perf: Add event descriptions References: <20150804001522.GA13214@dreric01-gentoo.localdomain> <20150817205809.GA16506@dreric01-gentoo.localdomain> <20150826165148.GF30466@arm.com> <20150817214035.GA25775@dreric01-gentoo.localdomain> <20150924175257.GH7356@arm.com> <20151007112011.GH16065@arm.com> In-Reply-To: <20151007112011.GH16065@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/2015 07:20 AM, Will Deacon wrote: > Hi again, Drew, > > On Thu, Sep 24, 2015 at 06:52:57PM +0100, Will Deacon wrote: >> On Mon, Aug 17, 2015 at 10:40:36PM +0100, Drew Richardson wrote: >>> So my suggestion to solve the problem is that the kernel can have the >>> list of events as proposed in the patch. >> >> Sorry, but I just don't buy this argument. Your problem is that the user >> needs to be running an up-to-date perf tool, but with your proposed >> solution, you're asking them to update the *kernel* instead, which is >> (unfortunately) one of the hardest pieces of software to upgrade on a >> typical ARM platform. > > I've spent some time thinking about this and, actually, it makes sense > to do this for the architected events. These event numbers are guaranteed > to be portable between CPUs, so if we expose those through sysfs then > we don't have this dependency on updating the kernel for newer cores > (well, once the initial period without your patch has expired). It's the > noon-portable, micro-architectural events that I object to. > > So how about you roll a new version of this patch just exposing the > architected events and making use of the macros in perf_event.h to make > it a bit tidier (PMU_EVENT_ATTR, PMU_EVENT_ATTR_STRING etc)? > > Be aware that there's a fair amount of arm64 perf patches queue for 4.4, > since we're moving over to the code in drivers/perf/. Hopefully these > will appear on the arm64 for-next/core branch shortly. Have you considered using OF/ACPI to describe this aspect of the hardware? Thanks, Christopher Covington -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project