From patchwork Fri May 13 11:39:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 12848708 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3027C433FE for ; Fri, 13 May 2022 11:42:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379937AbiEMLmO (ORCPT ); Fri, 13 May 2022 07:42:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379936AbiEMLmN (ORCPT ); Fri, 13 May 2022 07:42:13 -0400 Received: from conuserg-07.nifty.com (conuserg-07.nifty.com [210.131.2.74]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B635641611; Fri, 13 May 2022 04:42:10 -0700 (PDT) Received: from grover.sesame (133-32-177-133.west.xps.vectant.ne.jp [133.32.177.133]) (authenticated) by conuserg-07.nifty.com with ESMTP id 24DBeEwg008349; Fri, 13 May 2022 20:40:21 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-07.nifty.com 24DBeEwg008349 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1652442022; bh=tcr+72ZYpbdDhhd7b5O3qNkSWb92WQKtLNqtDxevyAs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OV1zKueC95HJzEs4YNsULTic+nna5e5ypNTY7m3NhIVfc2INdeDR+cF7c9HiKtmfO Qsxy9MeGttwP5DhD5nIjIGS6Jw3zwcorHMHHWVYJXiFYZuUK3k5q/BUSOsEBIqbT8G tGuZMPTt2WpKvva0OBHxCxS11/aJcwiPnkgM61RQAg73E0WcoRQSJTRSOy/3bOCVla QW2I/PD7vcNam1TYdRNs1sgpGDPvpJh0OJcetNEO9K2wXgxHC3AHv76hixXjfu06ul 6TB+psG90p2nRGU0R3CISH6Aixz7/sUjannthx6dJi3gpikM00BAsIF10kg0SIQGSy Dmy2tZFi5CnoQ== X-Nifty-SrcIP: [133.32.177.133] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nathan Chancellor , Nick Desaulniers , Nicolas Schier , Peter Zijlstra , linux-modules@vger.kernel.org, llvm@lists.linux.dev, Ard Biesheuvel , Sami Tolvanen , Masahiro Yamada Subject: [PATCH v6 07/10] kbuild: make built-in.a rule robust against too long argument error Date: Fri, 13 May 2022 20:39:27 +0900 Message-Id: <20220513113930.10488-8-masahiroy@kernel.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220513113930.10488-1-masahiroy@kernel.org> References: <20220513113930.10488-1-masahiroy@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: Kbuild runs at the top of objtree instead of changing the working directory to subdirectories. I think this design is nice overall but some commands have a scalability issue. The build command of built-in.a is one of them whose length scales with: O(D * N) Here, D is the length of the directory path (i.e. $(obj)/ prefix), N is the number of objects in the Makefile, O() is the big O notation. The deeper directory the Makefile directory is located, the more easily it will hit the too long argument error. We can make it better. Trim the $(obj)/ by Make's builtin function, and restore it by a shell command (sed). With this, the command length scales with: O(D + N) In-tree modules still have some room to the limit (ARG_MAX=2097152), but this is more future-proof for big modules in a deep directory. For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor --- (no changes since v2) Changes in v2: - New patch scripts/Makefile.build | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index c2a173b3fd60..8f1a355df7aa 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -374,7 +374,10 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; # quiet_cmd_ar_builtin = AR $@ - cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) + cmd_ar_builtin = rm -f $@; \ + echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \ + sed -E 's:([^ ]+):$(obj)/\1:g' | \ + xargs $(AR) cDPrST $@ $(obj)/built-in.a: $(real-obj-y) FORCE $(call if_changed,ar_builtin)