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 2F6B4C433EF for ; Fri, 17 Dec 2021 09:16:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234079AbhLQJQt (ORCPT ); Fri, 17 Dec 2021 04:16:49 -0500 Received: from mail.kdab.com ([176.9.126.58]:60120 "EHLO mail.kdab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234071AbhLQJQs (ORCPT ); Fri, 17 Dec 2021 04:16:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kdab.com; h= content-type:content-type:mime-version:references:in-reply-to :organization:message-id:date:date:subject:subject:from:from; s= dkim; t=1639732606; x=1640596607; bh=RIGIY/qzOCLdfvZtIgnf4aulM/8 dU67skFvF71qs9u0=; b=umWUk3qnqL94pWWPQUYLxthExOFzJdggLYPXUrViy19 QpYsHWQFp8TwLI7bxFhvOJ9veseznIqO1rHE9if7JcjEkvEYfncNfFRBqlc+A1oH aVcrPxAg8TZMSh39gLOs7hTVh9ybKbAh8Yl7Ouf29ZHYTlBCR/yVrK8rWD0U7ZJg = X-Virus-Scanned: amavisd-new at kdab.com From: Milian Wolff To: linux-perf-users@vger.kernel.org, Timothy Miller Subject: Re: perf not showing me call graph for memcpy no matter what Date: Fri, 17 Dec 2021 10:16:42 +0100 Message-ID: <234249826.y6c5yYTOUe@milian-workstation> Organization: KDAB In-Reply-To: <55BDE53A-EF97-4EF6-80C4-11821372A842@icloud.com> References: <55BDE53A-EF97-4EF6-80C4-11821372A842@icloud.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart4634325.yrQ3OjWpS4"; micalg="sha256"; protocol="application/pkcs7-signature" Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org --nextPart4634325.yrQ3OjWpS4 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" On Donnerstag, 16. Dezember 2021 14:37:03 CET Timothy Miller wrote: > Hi, >=20 > I am doing some software profiling on an aarch64 system, and I=E2=80=99m = using the > Linux perf tool. The problem I=E2=80=99m running into is that =E2=80=9C__= GI___memcpy_simd=E2=80=9D > keeps showing up as the function with the most CPU usage. >=20 > Unfortunately, no matter what I do, this function keeps showing up as > orphaned. That is, I cannot get a stack trace for it so I can find out who > is calling it. >=20 > I have tried using dwarf mode, but it always gets overloaded. >=20 > I have tried using lbr mode, but I get the following error: > Error: > PMU Hardware doesn't support sampling/overflow-interrupts. >=20 > I=E2=80=99ve rebuilt my application and all relevant libraries with > -no-omit-frame-pointer so that I could use the default frame pointer mode. > Unfortunately, I still can=E2=80=99t get a call graph for this function. >=20 > I emailed the glibc mailing list about this, trying to find out how to wo= rk > around this problem, perhaps adding frame pointer to the assembly > implementation of memcpy. They suggested I try attaching a debugger, and > I=E2=80=99ve found that I can get stack traces just fine. They suggest th= at I seem > to be running into some kind of bug in perf. >=20 > Any help/advice would be appreciated. Hey Timothy, I haven't been following upstream perf development closely in the past, but= a=20 few years ago perf was missing support for arm <-> x86 cross machine=20 unwinding. Maybe that's the issue you are running into? Can you try the AppImage of hotspot available at [1] and see if that one wo= rks=20 when you pass the right sysroot and potentially other flags, see [2] and=20 `hotspot --help` for more information. Hotspot uses a different unwinding mechanism and at least in the past used = to=20 be better at unwinding `perf.data` files recorded on arm on a x86 machine. One way or another though, it would be great if you can share an MWE - i.e.= =20 the `perf.data` file together with the `perf archive` for a minimal example= =20 that just calls `memcpy` in a loop. Cheers [1]: https://github.com/KDAB/hotspot/releases/tag/continuous [2]: https://github.com/KDAB/hotspot#embedded-systems =2D-=20 Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer KDAB (Deutschland) GmbH, a KDAB Group company Tel: +49-30-521325470 KDAB - The Qt, C++ and OpenGL Experts --nextPart4634325.yrQ3OjWpS4 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEekw ggWBMIIEaaADAgECAhA5ckQ6+SK3UdfTbBDdMTWVMA0GCSqGSIb3DQEBDAUAMHsxCzAJBgNVBAYT AkdCMRswGQYDVQQIDBJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcMB1NhbGZvcmQxGjAYBgNV BAoMEUNvbW9kbyBDQSBMaW1pdGVkMSEwHwYDVQQDDBhBQUEgQ2VydGlmaWNhdGUgU2VydmljZXMw HhcNMTkwMzEyMDAwMDAwWhcNMjgxMjMxMjM1OTU5WjCBiDELMAkGA1UEBhMCVVMxEzARBgNVBAgT Ck5ldyBKZXJzZXkxFDASBgNVBAcTC0plcnNleSBDaXR5MR4wHAYDVQQKExVUaGUgVVNFUlRSVVNU 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