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 38218C433E0 for ; Fri, 22 Jan 2021 01:49:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC147239A4 for ; Fri, 22 Jan 2021 01:49:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726402AbhAVBt4 (ORCPT ); Thu, 21 Jan 2021 20:49:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726044AbhAVBty (ORCPT ); Thu, 21 Jan 2021 20:49:54 -0500 Received: from mail-io1-xd2a.google.com (mail-io1-xd2a.google.com [IPv6:2607:f8b0:4864:20::d2a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DABDFC061756; Thu, 21 Jan 2021 17:49:13 -0800 (PST) Received: by mail-io1-xd2a.google.com with SMTP id d13so8142936ioy.4; Thu, 21 Jan 2021 17:49:13 -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=9/YkKKEDfJW7Vo1FQpb2GhjTxLI3VJ5grKY0rxpkAOU=; b=fVXDIODjghhQ8J486qs5R1GtmzhGk8/znAUIJiX9AA5vua65RtA8d+W0thhNFtOzrI 4cULncuCcGm8MpUvpy8MPnhptc4stA+wivWHaIQvVBmkDwGOMMi2eeiHNSt6fYEsHpBA mPDMVnmtYNuX8aRoYxhfpfFVB4dLw0XsNTScHtWsKUYJBIuA/ot3Swnly4pKS1sedmO6 8q4e5SptnMWyuHathEexDdrz9BPJnMPKbTRO+rQPS4UD8gdWF2y4QrLjlvLTYg8x/m5R SGlziY3QLz1JnUp7opEuoHWA9nrQAWGjiVIjDzFVej31pExPSTNF7GYNNDALWXP90Jd/ +nog== 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=9/YkKKEDfJW7Vo1FQpb2GhjTxLI3VJ5grKY0rxpkAOU=; b=HL0/U06rjSGidToZg8SFLwcsBcpZKn89PtIp4ujlEC0b5Jpi1DGQOEwI+htlhb33Bw H0NyFHvI0Wf3PYv9HY2YD6iLXwmHLfQPyIvlfZSQA7nmqNKL9oblb2TgylNAYdljU8Rv J7CFZh+gilwNI7YavbiAk07gl3vpMKL6b6FNqUuNY8T3O1TGLzMB0N2zfHVnfvvG8imp Sj3Wa4aG5EKBl/ZaW224tBMdwLUjC7cy38fGrC68hjkWwNb8dqzvpyrkkBUfQ6R4d91W S8LY5FetKURAMGcKihjDZ7Fud4ayo4viKVV3/njgFxunt9Ru8kjNw8pGyolQsDv8lVHS V6mA== X-Gm-Message-State: AOAM530ZVWlbEm6fl2LYpKtI8kspBn5xFmz1GqNXQ6jXI9qA0liW3BbP NLFsP8w49IOBxYZ+Y5ywsUUfjkHxG6MSylKOwq4= X-Google-Smtp-Source: ABdhPJz+PMH0WT1UNdUKDSO0Vh9Zc+ayL11dPzSPX8Ij933AftdBLbidcz5kCH7sJk8d08H0cqFiFjtV3RPp8jzPt50= X-Received: by 2002:a6b:90c4:: with SMTP id s187mr1780888iod.75.1611280153202; Thu, 21 Jan 2021 17:49:13 -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: Fri, 22 Jan 2021 02:49:00 +0100 Message-ID: Subject: Re: [PATCH v5] pgo: add clang's Profile Guided Optimization infrastructure To: Nick Desaulniers Cc: Bill Wendling , Jonathan Corbet , Masahiro Yamada , Linux Doc Mailing List , LKML , Linux Kbuild mailing list , Clang-Built-Linux ML , Andrew Morton , Nathan Chancellor , Sami Tolvanen , Fangrui Song Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Jan 22, 2021 at 2:43 AM Nick Desaulniers wrote: > > On Wed, Jan 20, 2021 at 6:03 PM 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? > > I was able to build+boot with LLVM_IAS=1 on my personal laptop (no > dwarf 5, just mainline+v5). > To clarify: I can build a PGO-enabled Linux-kernel and boot it. Afterwards generate a vmlinux.profdata. In a next step: A rebuild without PGO-Kconfig disabled + LLVM_IAS=1 does not boot. - Sedat - > > > > 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 agree, providing test results with patches that haven't landed yet > can cloud the interpretation of results. It would be helpful to drop > local patch sets before trying this. > > If the resulting image still isn't working for you, can you please > provide your config? Surely we'd be able to reproduce boot failures in > QEMU? Nothing comes to mind about a change of assemblers causing an > issue; I would assume assembly cannot be instrumented by the compiler > (even though the compiler is the "driver" of the assembler). > > The hash warnings are certainly curious. > IndexedInstrProfReader::getInstrProfRecord() is the only place in LLVM > sources that can emit that. > -- > Thanks, > ~Nick Desaulniers