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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 1705FC433DB for ; Thu, 21 Jan 2021 22:45:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D247D23A56 for ; Thu, 21 Jan 2021 22:45:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726194AbhAUWpd (ORCPT ); Thu, 21 Jan 2021 17:45:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbhAUWpX (ORCPT ); Thu, 21 Jan 2021 17:45:23 -0500 Received: from mail-io1-xd32.google.com (mail-io1-xd32.google.com [IPv6:2607:f8b0:4864:20::d32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A172DC06174A; Thu, 21 Jan 2021 14:44:43 -0800 (PST) Received: by mail-io1-xd32.google.com with SMTP id x21so7376256iog.10; Thu, 21 Jan 2021 14:44:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to:cc; bh=HvccmrfS5SgOEYdUs1blncI3hgFwaeqGnzFVcQFt3dc=; b=u1Qb7yOF9p/rb88qzEq4GviRLuH+MUSUAmAvzHLo5dvpmFP9zzB1w3jxT36IkT01MQ jitUXXbfbizxWQIi+aro8R5/RJaewpWWzpbgLwBMDylqZ8Sr2IWJESBKP7P/OKbJTY4N xLv7eyGHNVn7iv2If3D/zraYRTu67CNBtAaoV16zjOhdqrcgFa/sD2Qghn0LisjieqD0 Kd4kDONo8FAvJkN4eYazTWOfQ/bSzE3G7PaJTrUNbGP3mHfVcREyhK53vgvKc1Dt2pRN RWePftjwHAWfexMa1aInBwqJ3oil0f6Qr70oIyp/l7IvVt4arfrZVrqV8kAfkDuTgLTO kLmA== 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:reply-to :from:date:message-id:subject:to:cc; bh=HvccmrfS5SgOEYdUs1blncI3hgFwaeqGnzFVcQFt3dc=; b=YVgHCsH1FNNd4tSZ/s8X98eY7ijrbdrDCr56sgpIt5ctvyrt2BPGHnEXn7dLQne8E2 J9AjZHGhhHs4On85SO9p0iayLhGYXsjv1ZSCnA+wNay17wguPvrz/1VwQv9NhIynyWlN QSVbCRJ2CYzjP2hzZj/uWDLHquRxb3YQ8JcsKOai3jcunbohDxtB38C16ovklU8BKSiQ UISEDFVkk4mJJvD5SVHqLDIvTBKRX5pI0RTKk6ClbobwqkzTLuhmn2R06TZpsyGIY0SW p2uvxhbJ5dsGZlgAXDpA0aY7bvYIlp9RDgIEB8rrb7kFnFHznq7Hp2XFFJYEEDW6tOv1 jUAQ== X-Gm-Message-State: AOAM531QUuS9k32IJIQ5zFt3jpEabrWTWz+OqFqO6otBklBWIQo2Asnc tezzRF58WfxLQmftbThdYc7XZkZkr0+KwqwvkGTS4qWxeevMJYN5 X-Google-Smtp-Source: ABdhPJz43mrrriVp8Cqor+enuQGh/IB1IH0yc1vlFlsHxQTDHV/y7F+MU5VgTHcPTlbl3EyCA2T/f/E5BRMe/AQgz7Y= X-Received: by 2002:a6b:6a0e:: with SMTP id x14mr1296225iog.57.1611269083021; Thu, 21 Jan 2021 14:44:43 -0800 (PST) MIME-Version: 1.0 References: <20210113061958.886723-1-morbo@google.com> <20210116094357.3620352-1-morbo@google.com> In-Reply-To: Reply-To: sedat.dilek@gmail.com From: Sedat Dilek Date: Thu, 21 Jan 2021 23:44:31 +0100 Message-ID: Subject: Re: [PATCH v5] pgo: add clang's Profile Guided Optimization infrastructure To: Bill Wendling Cc: Jonathan Corbet , Masahiro Yamada , Linux Doc Mailing List , LKML , Linux Kbuild mailing list , Clang-Built-Linux ML , Andrew Morton , Nathan Chancellor , Nick Desaulniers , Sami Tolvanen , Fangrui Song Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, Jan 21, 2021 at 3:03 AM Sedat Dilek wrote: > > On Mon, Jan 18, 2021 at 10:56 PM Bill Wendling wrote: > > > > On Mon, Jan 18, 2021 at 9:26 AM Sedat Dilek wrote: > > > > > > On Mon, Jan 18, 2021 at 1:39 PM Sedat Dilek wrote: > > > > > > > > On Mon, Jan 18, 2021 at 3:32 AM Bill Wendling wrote: > > > > > > > > > > On Sun, Jan 17, 2021 at 4:27 PM Sedat Dilek wrote: > > > > > > > > > > > > [ big snip ] > > > > > > > > > > [More snippage.] > > > > > > > > > > > [ CC Fangrui ] > > > > > > > > > > > > With the attached... > > > > > > > > > > > > [PATCH v3] module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for > > > > > > undefined symbols > > > > > > > > > > > > ...I was finally able to boot into a rebuild PGO-optimized Linux-kernel. > > > > > > For details see ClangBuiltLinux issue #1250 "Unknown symbol > > > > > > _GLOBAL_OFFSET_TABLE_ loading kernel modules". > > > > > > > > > > > Thanks for confirming that this works with the above patch. > > > > > > > > > > > @ Bill Nick Sami Nathan > > > > > > > > > > > > 1, Can you say something of the impact passing "LLVM_IAS=1" to make? > > > > > > > > > > The integrated assembler and this option are more-or-less orthogonal > > > > > to each other. One can still use the GNU assembler with PGO. If you're > > > > > having an issue, it may be related to ClangBuiltLinux issue #1250. > > > > > > > > > > > 2. Can you please try Nick's DWARF v5 support patchset v5 and > > > > > > CONFIG_DEBUG_INFO_DWARF5=y (see attachments)? > > > > > > > > > > > I know Nick did several tests with PGO. He may have looked into it > > > > > already, but we can check. > > > > > > > > > > > > > Reproducible. > > > > > > > > LLVM_IAS=1 + DWARF5 = Not bootable > > > > > > > > I will try: > > > > > > > > LLVM_IAS=1 + DWARF4 > > > > > > > > > > I was not able to boot into such a built Linux-kernel. > > > > > PGO will have no effect on debugging data. If this is an issue with > > DWARF, then it's likely orthogonal to the PGO patch. > > > > > For me worked: DWARF2 and LLVM_IAS=1 *not* set. > > > > > > Of course, this could be an issue with my system's LLVM/Clang. > > > > > > Debian clang version > > > 12.0.0-++20210115111113+45ef053bd709-1~exp1~20210115101809.3724 > > > > > Please use the official clang 11.0.1 release > > (https://releases.llvm.org/download.html), modifying the > > kernel/pgo/Kconfig as I suggested above. The reason we specify clang > > 12 for the minimal version is because of an issue that was recently > > fixed. > > > > I downgraded to clang-11.1.0-rc1. > ( See attachment. ) > > Doing the first build with PGO enabled plus DWARF5 and LLVM_IAS=1 works. > > But again after generating vmlinux.profdata and doing the PGO-rebuild > - the resulting Linux-kernel does NOT boot in QEMU or on bare metal. > With GNU/as I can boot. > > So this is independent of DWARF v4 or DWARF v5 (LLVM_IAS=1 and DWARF > v2 is not allowed). > There is something wrong (here) with passing LLVM_IAS=1 to make when > doing the PGO-rebuild. > > Can someone please verify and confirm that the PGO-rebuild with > LLVM_IAS=1 boots or boots not? > > Thanks. > > - Sedat - > > > > Can you give me a LLVM commit-id where you had success with LLVM_IAS=1 > > > and especially CONFIG_DEBUG_INFO_DWARF5=y? > > > Success means I was able to boot in QEMU and/or bare metal. > > > > > The DWARF5 patch isn't in yet, so I don't want to rely upon it too much. > > I passed LLVM_IAS=1 with KAFLAGS=-fprofile-use=vmlinux.profdata: /usr/bin/perf_5.10 stat make V=1 -j4 HOSTCC=clang HOSTCXX=clang++ HOSTLD=ld.lld CC=clang LD=ld.lld PAHOLE=/opt/paho le/bin/pahole LOCALVERSION=-2-amd64-clang11-pgo KBUILD_VERBOSE=1 KBUILD_BUILD_HOST=iniza KBUILD_BUILD_USER=sedat.dilek@gmail.com KBUILD_BUILD_TIMESTAMP=2021-01-21 bind eb-pkg KDEB_PKGVERSION=5.11.0~rc4-2~bullseye+dileks1 LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata LLVM_IAS=1 KAFLAGS=-fprofile-use=vmlinux.profdata The resulting Linux-kernel does not boot. But I see in the build-log these warnings: warning: arch/x86/platform/efi/quirks.c: Function control flow change detected (hash mismatch) efi_arch_mem_reserve Hash = 73770966985 [-Wbackend-plugin] warning: arch/x86/platform/efi/efi.c: Function control flow change detected (hash mismatch) efi_attr_is_visible Hash = 57959232386 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) memcmp Hash = 12884901887 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) bcmp Hash = 12884901887 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strcmp Hash = 44149752232 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strnlen Hash = 29212902728 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) simple_strtoull Hash = 288230479369728480 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strstr Hash = 76464046323 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strchr Hash = 30948479515 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) kstrtoull Hash = 288230543187488006 [-Wbackend-plugin] What does "Function control flow change detected (hash mismatch)" mean? Related with my boot problems? - Sedat -