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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B814FC88E75 for ; Mon, 14 Sep 2026 15:09:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:References:In-Reply-To:Subject:Cc:To: From:Date:Message-ID:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ERfGCh8jilpudkd7y4bePzysxKLzqd0DvNomMI5wy+g=; b=HV3hV7HuC3Z69H QwkfPlF19rfUdj7X9KKpvKojo/u0WyNQa4Q2JOsb/JJCz+sOXQNYJbpXArqnz3grNNY7u35pfKZy6 GUqx22EmanezceTrMX8FuRFspalU98pDBjVp+u7Fv8NN4yx2SdVUoJeWn8MLQ625WduN6uaXPIrBH bZSqrnHO/jdYc6lJ1ZKWyp1Mqlc9rb82nKo5bsDezkWOZxl6yIwIXp61aOT8CLeAUk7nbNAlasokh px8m66Ga2ZTqZoSmxIE8q5a5bNm+qqfjiwc0etpV+S76dPKnb9CinUvvL3yZTGOz8F1UfbGKDdzXV nq/ljwf+HYD/MG0uob+Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x68Iu-000000047AP-0ubq; Mon, 14 Sep 2026 15:09:08 +0000 Received: from mail.stoffel.org ([172.104.24.175]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x68Iq-0000000479a-2J1S; Mon, 14 Sep 2026 15:09:06 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=stoffel.org; i=@stoffel.org; q=dns/txt; s=20250308; t=1789398143; h=mime-version : content-type : content-transfer-encoding : message-id : date : from : to : cc : subject : in-reply-to : references : from; bh=oMblGF1PmYRaqle4YPaaEqUlpIDejeN8jfSd3IyEo/E=; b=AlmtH9STTB3sBPP31THd4Ukf5Z6t561oZCkY6InocAjV6FJV0GlJpESrVaoEiZ4A2uvYj gSessr0w8EU13qxN0B+jYQ20yXsLhCqUZutbGy7AcGcD5CFenB+bVoo/1m8Bw/R1ZtoWetF sBmKOUI3nx0KxE7wUcDCF+5n4994xds9o7lSQH/T2399oBGJXN2k3kZ8PCGsCP8feOVSZt7 E2jqE9cJAeF1HOKpro5FXdEZy3YI3ScbXELaBw6grc9sla2gt2x7VXc0k45gBGa5H3OmWN9 QSHUKS/Lr8CJN8h1E+WssVpWqEPHuNKBoEAReWkV8A5H3NgyUYydzjMKYCNw== Received: from quad.stoffel.org (unknown [24.177.6.168]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by mail.stoffel.org (Postfix) with ESMTPSA id 96A101EC77; Mon, 14 Sep 2026 11:02:23 -0400 (EDT) Received: by quad.stoffel.org (Postfix, from userid 1000) id E573BA3288; Mon, 14 Sep 2026 11:02:22 -0400 (EDT) MIME-Version: 1.0 Message-ID: <27304.3198.867048.379684@quad.stoffel.home> Date: Mon, 14 Sep 2026 11:02:22 -0400 From: "John Stoffel" To: "Lorenzo Stoakes (ARM)" Cc: Linus Torvalds , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , Masahiro Yamada , Alexey Gladkov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Arnd Bergmann , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Ilias Apalodimas , Josh Poimboeuf , Peter Zijlstra , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , Onur =?iso-8859-1?Q?=D6zkan?= , Jonathan Corbet , Randy Dunlap , Kees Cook , "Gustavo A. R. Silva" , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, Jens Axboe , linux-hardening@vger.kernel.org X-Clacks-Overhead: GNU Terry Pratchett Subject: Re: [PATCH v2 11/21] kbuild: avoid re-running compiler and linker probes In-Reply-To: <20260914-build-speedup-v2-11-39817ec5db23@kernel.org> References: <20260914-build-speedup-v2-0-39817ec5db23@kernel.org> <20260914-build-speedup-v2-11-39817ec5db23@kernel.org> X-Mailer: VM 8.3.3snapshot under GNU Emacs 28.2 (x86_64-pc-linux-gnu) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260914_080904_812679_B115E6AC X-CRM114-Status: GOOD ( 20.18 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org >>>>> "Lorenzo" == Lorenzo Stoakes (ARM) writes: > Each kernel make invocation begins with ~30 compiler and linker runs each > of which performs duplicate probe for a number of compiler and linker > options. > This is useless work - the compiler and its version is known, so use these > to determine which options are available, once. > A convention already exists for this - CC_HAS_xxx, LD_HAS_xxx in Kconfig > files (for example, CC_HAS_COUNTED_BY), so convert these probes to Kconfig > options where appropriate. > This change avoids a sublte issue with ppc32 (big endian) - clang doesn't ^^^^^^ subtle > accept -fno-stack-clash-protection on this sub-target, so keep this option > in the Makefile. > With gcc and clang, defconfig and allmodconfig, the recorded command > lines are unchanged, a build with nothing to do rebuilds nothing and W=1 > continues to function correctly. > Doing this improves all builds, but has a particularly positive impact on > no-op builds (builds where nothing has changed). > Whole build, 128-thread Threadripper 9980X, best of N runs: > before after delta > ------------------------------- > x86 defconfig, no-op make, gcc 0.78s 0.60s -0.18s (-23%) > x86 defconfig, no-op make, clang 0.94s 0.66s -0.28s (-30%) > x86 defconfig, touch mm/vma.c, gcc 8.6s 8.5s -0.16s (-2%) > x86 defconfig, touch mm/vma.c, clang 8.0s 7.7s -0.24s (-3%) > x86 defconfig, clean, clang 29.8s 29.4s -0.37s (-1%) > x86 allmodconfig, no-op make, gcc 12.9s 12.7s -0.23s (-2%) > x86 allmodconfig, no-op make, clang 14.2s 13.9s -0.29s (-2%) > x86 allmodconfig, touch mm/vma.c, clang 32.2s 31.9s -0.30s (-1%) Are these deltas just per-patch, but cumulative with all the previous patches applied? _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv