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=-17.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 C345EC433E0 for ; Mon, 11 Jan 2021 21:05:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E7DC22D05 for ; Mon, 11 Jan 2021 21:05:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389300AbhAKVFE (ORCPT ); Mon, 11 Jan 2021 16:05:04 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38262 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389211AbhAKVFC (ORCPT ); Mon, 11 Jan 2021 16:05:02 -0500 Received: from mail-io1-xd2b.google.com (mail-io1-xd2b.google.com [IPv6:2607:f8b0:4864:20::d2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3441FC061786; Mon, 11 Jan 2021 13:04:22 -0800 (PST) Received: by mail-io1-xd2b.google.com with SMTP id z5so1114917iob.11; Mon, 11 Jan 2021 13:04:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=N/JvOTzwKH7g4yOdOBaQJ0iIJUcwItzyG+gczSopw4M=; b=OXMlL0nFMwpzNwC2f9hygACs5XEunTsQpb6aACMX25jkbji9m8sSHFDsmhnp3mPYlp SlLN/oThul0KAa75nH+HduGfoaUrlmvTnc+vUKl+0rGbgc9PQ13hqoHp30u4GxpuL5BC drCtzm7vvpXBrSy5FHkBMKMHqhi07+9SDjvB+edTg0vuNByQ1XXJtSM4S5c7ACOxUv+1 khCCeK7WSN1uAunAcFugHBzaLVFRJ0V1MDTo5e+bMSje1OnOcz3pvZ9GCoofCoaU0VKE deXhPop+4w63HKcMjfAM77cdGSdmE/mA7P9sgfumesBviMBDDnz3FP9zk/45zCJLsBGw vFKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=N/JvOTzwKH7g4yOdOBaQJ0iIJUcwItzyG+gczSopw4M=; b=FyCxhM7tkQqrj6xEjqLHUblB5ugP8tm0Pr4fCq3/lIwzV8r4Cy8AxjMG+ZmT6TcSzK eWpsHs4lzm5OQMXOUJ214UCi2SuvmEv2ilS81B0XhvZK1Iema6TPXLRZAFvHFr9TrYvq 0jZ/jRTelF1btZGtvJ9oK7Na+3fpprwrW7KAkB/w9IgQj80xLx6yVg2/b4bbgW09Yf6L Xv6c9p5HaDp/Z3Rxmw9lculaztcbzj2Ibu///hBifQEKViZfCcqoF60f5DeuIUV/oJNM OXjMkRIekPZhTkN5aNBD1AVuZjGK0mCjp31ICFBWWkpZpRXRYUpT7+qpvEp3HhuLuAn9 bBzA== X-Gm-Message-State: AOAM533rfYLdbfXWcmp1FwRqI9j3EvR68eCXj9iqAdVMT51DUCrLpA0V z9QiK50nwsiL2BAFHS1jExY= X-Google-Smtp-Source: ABdhPJzlX1J0Me+WPyfffdtszIDtkV578KtRvvz7AHXun8SDcNdQAuwilVMi0DH4aOhMBMS4yA17gw== X-Received: by 2002:a6b:b5d2:: with SMTP id e201mr858966iof.111.1610399061403; Mon, 11 Jan 2021 13:04:21 -0800 (PST) Received: from ubuntu-m3-large-x86 ([2604:1380:45f1:1d00::1]) by smtp.gmail.com with ESMTPSA id r9sm547004ill.72.2021.01.11.13.04.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Jan 2021 13:04:20 -0800 (PST) Date: Mon, 11 Jan 2021 14:04:18 -0700 From: Nathan Chancellor To: Bill Wendling Cc: Jonathan Corbet , Masahiro Yamada , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, Andrew Morton , Nick Desaulniers , Sami Tolvanen Subject: Re: [PATCH] pgo: add clang's Profile Guided Optimization infrastructure Message-ID: <20210111210418.GA3660906@ubuntu-m3-large-x86> References: <20210111081821.3041587-1-morbo@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210111081821.3041587-1-morbo@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 11, 2021 at 12:18:21AM -0800, Bill Wendling wrote: > From: Sami Tolvanen > > Enable the use of clang's Profile-Guided Optimization[1]. To generate a > profile, the kernel is instrumented with PGO counters, a representative > workload is run, and the raw profile data is collected from > /sys/kernel/debug/pgo/profraw. > > The raw profile data must be processed by clang's "llvm-profdata" tool before > it can be used during recompilation: > > $ cp /sys/kernel/debug/pgo/profraw vmlinux.profraw > $ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > > Multiple raw profiles may be merged during this step. > > The data can be used either by the compiler if LTO isn't enabled: > > ... -fprofile-use=vmlinux.profdata ... > > or by LLD if LTO is enabled: > > ... -lto-cs-profile-file=vmlinux.profdata ... > > This initial submission is restricted to x86, as that's the platform we know > works. This restriction can be lifted once other platforms have been verified > to work with PGO. > > Note that this method of profiling the kernel is clang-native and isn't > compatible with clang's gcov support in kernel/gcov. > > [1] https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization > > Signed-off-by: Sami Tolvanen > Co-developed-by: Bill Wendling > Signed-off-by: Bill Wendling I took this for a spin against x86_64_defconfig and ran into two issues: 1. https://github.com/ClangBuiltLinux/linux/issues/1252 There is also one in drivers/gpu/drm/i915/i915_query.c. For the time being, I added PGO_PROFILE_... := n for those two files. 2. After doing that, I run into an undefined function error with ld.lld. How I tested: $ make -skj"$(nproc)" LLVM=1 defconfig $ scripts/config -e PGO_CLANG $ make -skj"$(nproc)" LLVM=1 olddefconfig vmlinux all ld.lld: error: undefined symbol: __llvm_profile_instrument_memop >>> referenced by head64.c >>> arch/x86/kernel/head64.o:(__early_make_pgtable) >>> referenced by head64.c >>> arch/x86/kernel/head64.o:(x86_64_start_kernel) >>> referenced by head64.c >>> arch/x86/kernel/head64.o:(copy_bootdata) >>> referenced 2259 more times Local diff: diff --git a/drivers/char/Makefile b/drivers/char/Makefile index ffce287ef415..4b2f238770b5 100644 --- a/drivers/char/Makefile +++ b/drivers/char/Makefile @@ -4,6 +4,7 @@ # obj-y += mem.o random.o +PGO_PROFILE_random.o := n obj-$(CONFIG_TTY_PRINTK) += ttyprintk.o obj-y += misc.o obj-$(CONFIG_ATARI_DSP56K) += dsp56k.o diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile index e5574e506a5c..d83cacc79b1a 100644 --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -168,6 +168,7 @@ i915-y += \ i915_vma.o \ intel_region_lmem.o \ intel_wopcm.o +PGO_PROFILE_i915_query.o := n # general-purpose microcontroller (GuC) support i915-y += gt/uc/intel_uc.o \