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 3E730C433EF for ; Wed, 6 Apr 2022 13:49:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233740AbiDFNvx (ORCPT ); Wed, 6 Apr 2022 09:51:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58150 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233489AbiDFNvd (ORCPT ); Wed, 6 Apr 2022 09:51:33 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 926B35F9ADD; Wed, 6 Apr 2022 04:28:58 -0700 (PDT) Received: from fraeml741-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4KYMfk02mrz688JV; Wed, 6 Apr 2022 19:26:54 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml741-chm.china.huawei.com (10.206.15.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 6 Apr 2022 13:28:56 +0200 Received: from [10.47.80.129] (10.47.80.129) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 6 Apr 2022 12:28:56 +0100 Message-ID: <2139adb2-17be-761f-3c8d-e006fc2c4384@huawei.com> Date: Wed, 6 Apr 2022 12:28:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: perf tool: About "perf arm64: Inject missing frames when using 'perf record --call-graph=fp'" To: James Clark , CC: , "jolsa@kernel.org >> Jiri Olsa" , , Linux Kernel Mailing List , Arnaldo Carvalho de Melo References: <5f1d8b3f-0afa-2724-4ff1-f061939c68c5@huawei.com> <2dc4266f-02b1-0937-a884-dfa037cc7ffd@arm.com> From: John Garry In-Reply-To: <2dc4266f-02b1-0937-a884-dfa037cc7ffd@arm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.80.129] X-ClientProxiedBy: lhreml728-chm.china.huawei.com (10.201.108.79) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/04/2022 10:08, James Clark wrote: > > > On 05/04/2022 15:04, John Garry wrote: >> Hi Alexandre, >> >> I notice that with commit b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'") that I get messages spewing the console when running perf record+report, as below: >> >> john@ubuntu:~/linux$sudo tools/perf/perf record -ag fio null12.fio >> john@ubuntu:~/linux$sudo tools/perf/perf report > report >> unwind: can't read reg 29 >> unwind: can't read reg 29 >> unwind: can't read reg 29 >> unwind: can't read reg 29 >> ... >> >> Do you know the possible cause? I haven't checked... > > Hi John, > > I'm going to look into this today. Great I expect the cause is because we only record >> the link register for this change and then do a best effort unwind to see if > we can get the return address just from that. So I don't think this is a major issue, > probably the outcome will be that I mask any of these errors just for this call > to libunwind that we added. The other main call to libunwind should still print > these errors. > > One thing that is interesting is why we didn't see this when we were testing > the patch before, and we've also found it a little bit difficult to reproduce here. > So there might be more to it than just masking the error, but I'm not sure yet. > > Either way, I don't expect that any unwinding is broken, just that it's > printing an annoying message. Yeah, the actual ouput looks ok at a glance. I really didn't check much. Thanks, John