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 BE183C04A68 for ; Thu, 28 Jul 2022 12:29:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238550AbiG1M3G (ORCPT ); Thu, 28 Jul 2022 08:29:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237660AbiG1M3E (ORCPT ); Thu, 28 Jul 2022 08:29:04 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 31E4161734; Thu, 28 Jul 2022 05:29:04 -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 72FFE106F; Thu, 28 Jul 2022 05:29:04 -0700 (PDT) Received: from [10.1.31.137] (e127744.cambridge.arm.com [10.1.31.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 709313F73B; Thu, 28 Jul 2022 05:29:02 -0700 (PDT) Subject: Re: [PATCH] perf/tests: Fix test case 95 on s390 and use same event To: Thomas Richter , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, acme@kernel.org, james.clark@arm.com Cc: svens@linux.ibm.com, gor@linux.ibm.com, sumanthk@linux.ibm.com, hca@linux.ibm.com, Namhyung Kim , Jiri Olsa References: <20220727141439.712582-1-tmricht@linux.ibm.com> <3dc28d5e-46ce-fd33-82c1-4e27b60dfef0@arm.com> <550e7e9f-19cb-0b1f-fd3e-f0d958b4e75b@linux.ibm.com> From: German Gomez Message-ID: <3cb2c002-e4e3-c7b4-148d-5e2d0c406b84@arm.com> Date: Thu, 28 Jul 2022 13:28:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <550e7e9f-19cb-0b1f-fd3e-f0d958b4e75b@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/07/2022 13:20, Thomas Richter wrote: > On 7/28/22 11:25, German Gomez wrote: >> Thanks for the fix, Thomas >> >> On 27/07/2022 15:14, Thomas Richter wrote: >>> On linux-next tree perf test 95 was added recently. >>> s390 does not support branch sampling at all and the test case fails >>> despite for checking branch support before hand. >>> The check for support of branching >>> uses the software event named dummy, as seen in the line: >>> >>> perf record -b -o- -e dummy -B true > /dev/null 2>&1 || exit 2 >> Just curious, do you know why the command succeeds in this platform (and >> potentially others)? >> >> I got the idea of using "dummy" from [1] but only tested on arm64 and >> x86. I thought the platforms would reject it if -b was not implemented >> regardless of the event. Did I misunderstand the use of dummy? >> >> Thanks, >> German >> >> [1] https://lore.kernel.org/all/20220617073840.GA45710@leoy-ThinkPad-X240s/ >> > Well, dummy is a predefined event of type software, you see that when you add > some -v options as in > # perf record -e dummy -vvv > DEBUGINFOD_URLS= > Using CPUID IBM,3931,704,A01,3.7,002f > nr_cblocks: 0 > affinity: SYS > mmap flush: 1 > comp level: 0 > ------------------------------------------------------------ > perf_event_attr: > type 1 <----------- type 1 is software > size 128 > config 0x9 > { sample_period, sample_freq } 4000 > > > So this event is never sent to an hardware PMU (which would have type 0) and thus > mostly succeeds where as the perf record command without event uses default > event cycles. And that one is sent to hardware PMU on s390... Thanks for explaining! My bad for missing this. Acked-by: German Gomez >