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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36AA0C11F67 for ; Tue, 29 Jun 2021 22:04:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 15BCA61D9F for ; Tue, 29 Jun 2021 22:04:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235284AbhF2WHN (ORCPT ); Tue, 29 Jun 2021 18:07:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234953AbhF2WHM (ORCPT ); Tue, 29 Jun 2021 18:07:12 -0400 Received: from mail-ej1-x62d.google.com (mail-ej1-x62d.google.com [IPv6:2a00:1450:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 962CCC061760 for ; Tue, 29 Jun 2021 15:04:44 -0700 (PDT) Received: by mail-ej1-x62d.google.com with SMTP id b2so488577ejg.8 for ; Tue, 29 Jun 2021 15:04:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Kpsr/FtbpsGhngyVxXXIyq1SDK1oPHQRTq+LLV3RKrw=; b=fvKRMzIgXBVRWCquKoY2dVqVG6FbFRKPzRAC5insxR9tsKcDAGFi7WDOxoK9YQSTX5 fetZ+gSSB7cTVIv9Ry1lOEaGDk6nYKFVIbx0JY14z3TboccJBsMyX3w+Fqd83bB5e0wJ ez+H/eSUFK5uLi9Z6IHqIZ6nKxbzRTkwTnhK8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Kpsr/FtbpsGhngyVxXXIyq1SDK1oPHQRTq+LLV3RKrw=; b=SBWisjsKhvSmEpmE5cx6BKe00AdutkM3FoDvF99u4AbAJmyMN+d3IzP/VhBicsUYDT NsuLmVPI0CeTtr9mV+Ep1s0JKHNZ/CFxSL/8GkXnbAvuWH9uOC/pCWNWdxeYqhWaYhQK kU36kBsaeBaG+SrGgTlMhHAfn5QeNJFDl6kCRzTxZI+3TAf1cOVSYPYXBNrQfO7pPkib N0V/iDz+XmENxw/coQ+k0Pp2pr6XSNGdDtHlWnfXF+kPPVQVH+QIa2/JsonhEGfd9KOX jwe8R7bklT3hTqBWr0Z9W9W6HUC2cAlx099WiU4ENXPEkdF01VEl1p6vJnud/iRFDmov 28OQ== X-Gm-Message-State: AOAM530euPpzVZpG7CwekFbltq8xsVKttN4a5GCXjQM809fsa2oJMcnL WCbmgI2VMDz4G/gd7wCqO5L23ngPXZqMwVCHSsQ= X-Google-Smtp-Source: ABdhPJxwi0cYXBDnM7GeaKXV/5WZMYjdU1wK1HZPXcVEIu0bTIQHqLmCWH1ConAX8ER9lvs6v/XkBQ== X-Received: by 2002:a17:906:25cb:: with SMTP id n11mr32173066ejb.539.1625004283037; Tue, 29 Jun 2021 15:04:43 -0700 (PDT) Received: from mail-ej1-f52.google.com (mail-ej1-f52.google.com. [209.85.218.52]) by smtp.gmail.com with ESMTPSA id f3sm8970092ejl.29.2021.06.29.15.04.42 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Jun 2021 15:04:42 -0700 (PDT) Received: by mail-ej1-f52.google.com with SMTP id hc16so450750ejc.12 for ; Tue, 29 Jun 2021 15:04:42 -0700 (PDT) X-Received: by 2002:a05:651c:32e:: with SMTP id b14mr5398881ljp.251.1625003885865; Tue, 29 Jun 2021 14:58:05 -0700 (PDT) MIME-Version: 1.0 References: <202106281231.E99B92BB13@keescook> <202106291311.20AB10D04@keescook> In-Reply-To: From: Linus Torvalds Date: Tue, 29 Jun 2021 14:57:49 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] Clang feature updates for v5.14-rc1 To: Nick Desaulniers Cc: Kees Cook , Linux Kernel Mailing List , Bill Wendling , Bill Wendling , Catalin Marinas , clang-built-linux , Fangrui Song , Heiko Carstens , Jarmo Tiitto , Lukas Bulwahn , Mark Rutland , Masahiro Yamada , Miguel Ojeda , Nathan Chancellor , Peter Oberparleiter , Peter Zijlstra , Sami Tolvanen , Will Deacon Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 29, 2021 at 2:27 PM Nick Desaulniers wrote: > > Right now we're having trouble with hardware performance counters on > non-intel chips; I don't think we have working LBR equivalents on AMD > until zen3, and our ETM based samples on ARM are hung up on a few last > minute issues requiring new hardware (from multiple different chipset > vendors). I agree that perf profiling works best on Intel. The AMD perf side works ok in Zen 2 from what I've seen, but needs to be a full-system profile ("perf record -a") to use the better options, and ARM is.. But with x86 ranging from "excellent" to "usable", and ARM hopefully being at least close to getting better proper profile data, I really think it's the way forward, with instrumentation being a band-aid at best. Linus