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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 A45EDC48BD1 for ; Thu, 10 Jun 2021 18:44:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C87A606A5 for ; Thu, 10 Jun 2021 18:44:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230450AbhFJSqa (ORCPT ); Thu, 10 Jun 2021 14:46:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230329AbhFJSq3 (ORCPT ); Thu, 10 Jun 2021 14:46:29 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 767E6C061574 for ; Thu, 10 Jun 2021 11:44:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Av0VDrjTWxCk/CljDRNDCub1sCxNvQ1GxDN3sYJG65M=; b=niWX7k/KRIxm8S3HH4i6O4aGTh cv+FlKwCelbEa3wtyOp78bLtmKd6uQBKRhvaxuPNFXRVuvWstyN9GgjBzrUM0Uwz1vRdsrhXrYR2b gI1UPvTT9Rykh9x1rfONypIpK0/BVD7JTLHLE5MTBUh7JHBZs37eIv/B9LYNO8PC0f4OoOWsWPQ40 fk2X/eIC0uZTLfQwXbCWZLBEzTVtJf/2JyC0McXV61Ikb9O/wDrrdvWYiFHrWBhrdeVASUoIl7ptN /V/m2moTeLh0SofgoOKuKaX5WefIWmIyzkUrjFMIswcMTDyXXQBQM9ZtMtsSiK30C98f/aT59hUOJ zGVGFHjw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lrPec-001wgL-Js; Thu, 10 Jun 2021 18:43:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 603AA3001E3; Thu, 10 Jun 2021 20:43:45 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4078520299B51; Thu, 10 Jun 2021 20:43:45 +0200 (CEST) Date: Thu, 10 Jun 2021 20:43:45 +0200 From: Peter Zijlstra To: Nathan Chancellor Cc: x86@kernel.org, jpoimboe@redhat.com, jbaron@akamai.com, rostedt@goodmis.org, ardb@kernel.org, linux-kernel@vger.kernel.org, samitolvanen@google.com, ndesaulniers@google.com, clang-built-linux@googlegroups.com Subject: Re: [PATCH 01/13] objtool: Rewrite hashtable sizing Message-ID: References: <20210506193352.719596001@infradead.org> <20210506194157.452881700@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 10, 2021 at 11:14:51AM -0700, Nathan Chancellor wrote: > This patch as commit 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing") > in -tip causes a massive compile time regression with allmodconfig + > ThinLTO. Moo... the allyesconfig builds I used it on were much faster, but that was on regular GCC vmlinux.o after linking. > Adding Sami because I am not sure why this patch would have much of an impact > in relation to LTO. https://git.kernel.org/tip/25cf0d8aa2a3 is the patch in > question. > > If I can provide any further information or help debug, please let me know. > > If you are interested in reproducing this locally, you will need a > fairly recent LLVM stack (I used the stable release/12.x branch) and to > cherry-pick commit 976aac5f8829 ("kcsan: Fix debugfs initcall return > type") to fix an unrelated build failure. My script [2] can build a > self-contained toolchain fairly quickly if you cannot get one from your > package manager. A command like below will speed up the build a bit: Would something like llvm-13 from Debian be good enough? $ clang-13 --version Debian clang version 13.0.0-++20210418105309+a0898f0cecc7-1~exp1 Target: x86_64-pc-linux-gnu Thread model: posix InstalledDir: /usr/bin