From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C45AC43334 for ; Fri, 1 Jul 2022 17:20:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232179AbiGARUR (ORCPT ); Fri, 1 Jul 2022 13:20:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232086AbiGARUP (ORCPT ); Fri, 1 Jul 2022 13:20:15 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1743B2E6BF for ; Fri, 1 Jul 2022 10:20:13 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DFB54113E; Fri, 1 Jul 2022 10:20:12 -0700 (PDT) Received: from [10.1.196.218] (eglon.cambridge.arm.com [10.1.196.218]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4B5D33F792; Fri, 1 Jul 2022 10:20:11 -0700 (PDT) Subject: Re: [PATCH RESEND] perf/marvell_cn10k: Add MPAM support for TAD PMU To: Tanmay Jagdale , Robin Murphy , Will Deacon Cc: "mark.rutland@arm.com" , "robh@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Sunil Kovvuri Goutham , Linu Cherian , Bharat Bhushan , Amit Singh Tomar References: From: James Morse Message-ID: <72856daa-ef83-caee-b0d0-6b5018d1bafa@arm.com> Date: Fri, 1 Jul 2022 18:20:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tanmay, On 27/06/2022 14:18, Tanmay Jagdale wrote: >> On 2022-06-24 13:14, Will Deacon wrote: >>> On Sat, May 28, 2022 at 12:26:47AM +0530, Tanmay Jagdale wrote: >>>> The TAD PMU supports following counters that can be filtered by MPAM >>>> partition id. >>>> - (0x1a) tad_alloc_dtg : Allocations to DTG. >>>> - (0x1b) tad_alloc_ltg : Allocations to LTG. >>>> - (0x1c) tad_alloc_any : Total allocations to DTG/LTG. >>>> - (0x1d) tad_hit_dtg : DTG hits. >>>> - (0x1e) tad_hit_ltg : LTG hits. >>>> - (0x1f) tad_hit_any : Hit in LTG/DTG. >>>> - (0x20) tad_tag_rd : Total tag reads. >>>> >>>> Add a new 'partid' attribute of 16-bits to get the partition id >>>> passed from perf tool. This value would be stored in config1 field >>>> of perf_event_attr structure. >>>> >>>> Example: >>>> perf stat -e tad/tad_alloc_any,partid=0x12/ >>>> >>>> - Drop read of TAD_PRF since we don't have to preserve any >>>> bit fields and always write an updated value. >>>> - Update register offsets of TAD_PRF and TAD_PFC. >>> >>> It would be great if you could document some of this under >>> Documentation/admin-guide/perf like many of the other PMU drivers have >>> done. >> >> Especially documenting how the user obtains the required partid value to >> pass. > We created MPAM partitions using the resctrl filesystem interface. > Example: > $ cd /sys/fs/resctrl > $ mkdir p1 > $ echo "L3:0=f" > p1/schemata (configure 4 L3 cache ways) > $ mkdir p2 > $ echo "L3:1=ff0" > p2/schemata (configure 8 L3 cache ways) > > Here directory name 'p1' creates a MPAM partid 0x1 and 'p2' creates > 0x2 and so on. You can't rely on this. See the KNOWN_ISSUES file in the the mpam tree: PARTID 0 should be reserved for unknown hardware. In fact any number of PARTID may be reserved for in-kernel users. You can't guess what the offset might be from user-space. > Right now, there is no file which exposes the partid to userspace. > We must rely on the sequential order in which we create partitions > via resctrl and use that to derive the partid. If you dig in the MPAM tree you'll find how I intend to solve this for exposing the MPAM counters via perf. But this is a user-space visible change to resctrl, so it will need to wait until all the refactoring is done and the bulk of the MPAM driver is upstream. Thanks, James