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 85055C61D90 for ; Tue, 21 Nov 2023 16:08:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233946AbjKUQJA (ORCPT ); Tue, 21 Nov 2023 11:09:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229514AbjKUQI5 (ORCPT ); Tue, 21 Nov 2023 11:08:57 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7C611188; Tue, 21 Nov 2023 08:08:53 -0800 (PST) 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 105321FB; Tue, 21 Nov 2023 08:09:40 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.34.196]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1F8BD3F6C4; Tue, 21 Nov 2023 08:08:52 -0800 (PST) Date: Tue, 21 Nov 2023 16:08:49 +0000 From: Mark Rutland To: Ian Rogers Cc: Marc Zyngier , Hector Martin , Arnaldo Carvalho de Melo , James Clark , linux-perf-users@vger.kernel.org, LKML , Asahi Linux Subject: Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5 Message-ID: References: <08f1f185-e259-4014-9ca4-6411d5c1bc65@marcan.st> <86pm03z0kw.wl-maz@kernel.org> <86o7fnyvrq.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 21, 2023 at 08:03:11AM -0800, Ian Rogers wrote: > On Tue, Nov 21, 2023 at 7:56 AM Mark Rutland wrote: > > > > On Tue, Nov 21, 2023 at 07:41:17AM -0800, Ian Rogers wrote: > > > Hi Marc, > > > > Hi Ian, > > > > > I'm unclear if you are running a newer perf tool on an older kernel or > > > not. In any case I'll assume the kernel and perf tool versions match. > > > In Linux 6.6 this patch was added to the ARM PMU: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/perf/arm_pmu.c?id=5c816728651ae425954542fed64d21d40cb75a9f > > > > > > My guess is that the apple_icestorm_pmu requires a similar patch. > > > > The apple_icestorm_pmu PMU driver uses the arm_pmu framework, so it's using > > that code (since v6.6). > > > > > The perf tool is supposed to not use extended types when they aren't > > > supported: > > > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/pmus.c?h=perf-tools-next#n532 > > > > How does that is_event_supported() check actually work? I suspect that's giving > > the wrong answer. > > Maybe, the implementation is to check using perf_event_open: > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/print-events.c?h=perf-tools-next#n232 > > This is recycling logic from perf list where many legacy cache events > are elided due to a lack of support. > > > Regardless, I think the tool is doing something semantically wrong, see below. > > > > > So I share your confusion as to why something broke. > > > > > > PERF_TYPE_HARDWARE is a legacy type where there are hardcoded type and > > > config values that correspond to an event. The PMU driver turns legacy > > > events into the real types. On BIG.little systems if the legacy events > > > are monitoring a task a different event is needed for each PMU (ie >1 > > > event). In your example you are monitoring 'ls', a task, and so > > > different cycles events are necessary. In the high 32-bits (the > > > extended type) the PMU is identified. > > > > I think the interesting thing here is that the tool is mapping events with an > > explicit PMU into legacy PERF_TYPE_HARDWARE events, which is the opposite > > direction than intended. Regardless of whether PERF_TYPE_HARDWARE events can be > > targetted to a specific PMU, if the user has requested to use a specific PMU we > > should be using that PMU and related event namespace. > > > > Marc's command line was: > > > > sudo taskset -c 0 ./perf stat -vvv \ > > -e apple_icestorm_pmu/cycles/ \ > > -e apple_firestorm_pmu/cycles/ \ > > -e cycles \ > > -e cycles here is a direct request for the legacy cycles event. It > will match in the parser here: > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/parse-events.l?h=perf-tools-next#n301 > > which goes to: > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/parse-events.y?h=perf-tools-next#n397 > > and as this is a hardware event there is wildcard expansion on each core PMU. Please read the rest of my message, which was talking about the other two events. Mark. > > Thanks, > Ian > > > ls > > > > ... and so the apple_*_pmu events should target their respective PMUs, and the > > plain 'cycles' event could legitimately be opened as a single > > PERF_TYPE_HARDWARE event, or split into two directed PERF_TYPE_HARDWARE events > > targetting the two PMUs. > > > > However, thwe tool opens three (undirected?) PERF_TYPE_HARDWARE events: > > > > Opening: apple_icestorm_pmu/cycles/ > > ------------------------------------------------------------ > > perf_event_attr: > > type 0 (PERF_TYPE_HARDWARE) > > size 136 > > config 0 (PERF_COUNT_HW_CPU_CYCLES) > > sample_type IDENTIFIER > > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING > > disabled 1 > > inherit 1 > > enable_on_exec 1 > > exclude_guest 1 > > ------------------------------------------------------------ > > sys_perf_event_open: pid 1045843 cpu -1 group_fd -1 flags 0x8 = 3 > > Opening: apple_firestorm_pmu/cycles/ > > ------------------------------------------------------------ > > perf_event_attr: > > type 0 (PERF_TYPE_HARDWARE) > > size 136 > > config 0 (PERF_COUNT_HW_CPU_CYCLES) > > sample_type IDENTIFIER > > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING > > disabled 1 > > inherit 1 > > enable_on_exec 1 > > exclude_guest 1 > > ------------------------------------------------------------ > > sys_perf_event_open: pid 1045843 cpu -1 group_fd -1 flags 0x8 = 4 > > Opening: cycles > > ------------------------------------------------------------ > > perf_event_attr: > > type 0 (PERF_TYPE_HARDWARE) > > size 136 > > config 0 (PERF_COUNT_HW_CPU_CYCLES) > > sample_type IDENTIFIER > > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING > > disabled 1 > > inherit 1 > > enable_on_exec 1 > > exclude_guest 1 > > ------------------------------------------------------------ > > > > Mark.