Received: by 2002:a6b:fb09:0:0:0:0:0 with SMTP id h9csp2974053iog; Mon, 20 Jun 2022 08:34:09 -0700 (PDT) X-Google-Smtp-Source: AGRyM1u54hL1tJ/HK2q1x3cJ5osk+riy75Gv6TCwo/mavqOIQ4atx5lgQkijEQyT2Cm/UGKdL9d7 X-Received: by 2002:a5d:5181:0:b0:20f:fc49:6b88 with SMTP id k1-20020a5d5181000000b0020ffc496b88mr22865069wrv.596.1655739249162; Mon, 20 Jun 2022 08:34:09 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1655739249; cv=none; d=google.com; s=arc-20160816; b=BbWp/nJb7qoC2bO4Ogp6nA5nYLdPZHjZEKR8hXafPiiKtcVyDqu/MnxIqRv6dhWlwY 697y1Bm6liIWG2yy36PphV21jJ423hnza0Mwox5uYB/SLh2bvTEv8ZOlT4TbitNKdlZm Fh1YQEAyWW2B38JrIw7JLjFT1v8rOH2D/c3+TjOLyxawPAHsdVqC8YUQNaOcwLEcZlZ4 axNHmpusvn8gTcfs2MxFXEMUYseQ38S2yihHQ3hSrGqeun3O4eteZ669/Y0rtFhcln8b d+cV3P4JvNB3j30Znxbnl9NGca1rvHyHKLZcVePhaxP+GFDBJbx8fYk7SCuhkFnzNWpn NR9A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=I3THVVtcZF+jcypHfxpYOH+9vAuK9IzGCXwnEeMY8aw=; b=OXmdqZ3+b738cMBUAbVXrg7Ww/GkqxhqiDZAMSdwy2Wgo4CeDGlRVgL0FBjmNe0e4+ dfEPfQadZ3NB0Cv+0AXW/E8mc2oTeFw0M+0HWSt1CaKNx3SqE+2awXw+oLCcIrDwHk0c tPSdBHwotwm6fNksYk1v15fM53JW1jVKfqnRxff3AGPR6/jKL2ua9PA8dE0GjKwt1tfH BWiDi3sySpfynmIvY2suF+yuW1gXTX+xL0bHVTbvb6M5PvYunlL4xYe/vaHZFmUEZ9RF xiSmcZxiVGrVWf8tLcSyb6SRY/si2QSrgf/gOBe4GsQeS4YuUm7s5kLQGjYpUDeMb94b lUuA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=U7x2ZlFb; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Return-Path: Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id bz14-20020a056000090e00b0021b85c2fa87si9763343wrb.92.2022.06.20.08.33.40; Mon, 20 Jun 2022 08:34:09 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=U7x2ZlFb; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243841AbiFTPYA (ORCPT + 99 others); Mon, 20 Jun 2022 11:24:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245388AbiFTPXh (ORCPT ); Mon, 20 Jun 2022 11:23:37 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22EE92DFD; Mon, 20 Jun 2022 08:20:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1655738424; x=1687274424; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Cw5NQyynR7ghE5FtblfyyewHSqrS21SURI3e+e9d2nU=; b=U7x2ZlFbbCvxPQtxw2xwS9g7nOoNFhzOEr4XHlyYCmkzssIM424pCIFm fYALvqkjLYEnmbCeCAriXNLqidesZaZIpHyi3wVN5Foi9mablDSTLWedM z8snqyp1arXVYUkq+WBZq7igCl+zIr2fmgJJeA0dLzn6D5bwsb7OIIlKf 134fGgIpYI7uGb2VaOROGvaqbzB7mkwJUyI2bQ7wr/v/GpK4zUKTsb1oK RuWQ4dqpigsMLNp0q4Z4hP95ttPg14vSLOCQPqopXPXjlSRCyGxlN5TQb CSLuoS+9YLRwVdR25SFez+Dy80QZ3xFh4kFVoOvbAhAqhSEpyMNZmYnN3 g==; X-IronPort-AV: E=McAfee;i="6400,9594,10384"; a="262955342" X-IronPort-AV: E=Sophos;i="5.92,207,1650956400"; d="scan'208";a="262955342" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jun 2022 08:20:23 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.92,207,1650956400"; d="scan'208";a="643166185" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by fmsmga008.fm.intel.com with ESMTP; 20 Jun 2022 08:20:17 -0700 Received: from newjersey.igk.intel.com (newjersey.igk.intel.com [10.102.20.203]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 25KFKF3L026144; Mon, 20 Jun 2022 16:20:15 +0100 From: Alexander Lobakin To: Mark Rutland Cc: Alexander Lobakin , Arnd Bergmann , Yury Norov , "Andy Shevchenko" , Matt Turner , Brian Cain , Geert Uytterhoeven , Yoshinori Sato , "Rich Felker" , "David S. Miller" , Kees Cook , "Peter Zijlstra (Intel)" , Marco Elver , Borislav Petkov , Tony Luck , Maciej Fijalkowski , Jesse Brandeburg , Greg Kroah-Hartman , linux-alpha@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/7] bitops: let optimize out non-atomic bitops on compile-time constants Date: Mon, 20 Jun 2022 17:08:55 +0200 Message-Id: <20220620150855.2630784-1-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: References: <20220617144031.2549432-1-alexandr.lobakin@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mark Rutland Date: Mon, 20 Jun 2022 15:19:42 +0100 > On Fri, Jun 17, 2022 at 04:40:24PM +0200, Alexander Lobakin wrote: > > So, in order to let the compiler optimize out such cases, expand the > > test_bit() and __*_bit() definitions with a compile-time condition > > check, so that they will pick the generic C non-atomic bitop > > implementations when all of the arguments passed are compile-time > > constants, which means that the result will be a compile-time > > constant as well and the compiler will produce more efficient and > > simple code in 100% cases (no changes when there's at least one > > non-compile-time-constant argument). > > > The savings are architecture, compiler and compiler flags dependent, > > for example, on x86_64 -O2: > > > > GCC 12: add/remove: 78/29 grow/shrink: 332/525 up/down: 31325/-61560 (-30235) > > LLVM 13: add/remove: 79/76 grow/shrink: 184/537 up/down: 55076/-141892 (-86816) > > LLVM 14: add/remove: 10/3 grow/shrink: 93/138 up/down: 3705/-6992 (-3287) > > > > and ARM64 (courtesy of Mark[0]): > > > > GCC 11: add/remove: 92/29 grow/shrink: 933/2766 up/down: 39340/-82580 (-43240) > > LLVM 14: add/remove: 21/11 grow/shrink: 620/651 up/down: 12060/-15824 (-3764) > > Hmm... with *this version* of the series, I'm not getting results nearly as > good as that when building defconfig atop v5.19-rc3: > > GCC 8.5.0: add/remove: 83/49 grow/shrink: 973/1147 up/down: 32020/-47824 (-15804) > GCC 9.3.0: add/remove: 68/51 grow/shrink: 1167/592 up/down: 30720/-31352 (-632) > GCC 10.3.0: add/remove: 84/37 grow/shrink: 1711/1003 up/down: 45392/-41844 (3548) > GCC 11.1.0: add/remove: 88/31 grow/shrink: 1635/963 up/down: 51540/-46096 (5444) > GCC 11.3.0: add/remove: 89/32 grow/shrink: 1629/966 up/down: 51456/-46056 (5400) > GCC 12.1.0: add/remove: 84/31 grow/shrink: 1540/829 up/down: 48772/-43164 (5608) > > LLVM 12.0.1: add/remove: 118/58 grow/shrink: 437/381 up/down: 45312/-65668 (-20356) > LLVM 13.0.1: add/remove: 35/19 grow/shrink: 416/243 up/down: 14408/-22200 (-7792) > LLVM 14.0.0: add/remove: 42/16 grow/shrink: 415/234 up/down: 15296/-21008 (-5712) > > ... and that now seems to be regressing codegen with recent versions of GCC as > much as it improves it LLVM. > > I'm not sure if we've improved some other code and removed the benefit between > v5.19-rc1 and v5.19-rc3, or whether something else it at play, but this doesn't > look as compelling as it did. Mostly likely it's due to that in v1 I mistakingly removed `volatile` from gen[eric]_test_bit(), so there was an impact for non-constant cases as well. +5 Kb sounds bad tho. Do you have CONFIG_TEST_BITMAP enabled, does it work? Probably the same reason as for m68k, more constant optimization -> more aggressive inlining or inlining rebalance -> larger code. OTOH I've no idea why sometimes compiler decides to uninline really tiny functions where due to this patch series some bitops have been converted to constants, like it goes on m68k. > > Overall that's mostly hidden in the Image size, due to 64K alignment and > padding requirements: > > Toolchain Before After Difference > > GCC 8.5.0 36178432 36178432 0 > GCC 9.3.0 36112896 36112896 0 > GCC 10.3.0 36442624 36377088 -65536 > GCC 11.1.0 36311552 36377088 +65536 > GCC 11.3.0 36311552 36311552 0 > GCC 12.1.0 36377088 36377088 0 > > LLVM 12.0.1 31418880 31418880 0 > LLVM 13.0.1 31418880 31418880 0 > LLVM 14.0.0 31218176 31218176 0 > > ... so aside from the blip around GCC 10.3.0 and 11.1.0, there's not a massive > change overall (due to 64KiB alignment restrictions for portions of the kernel > Image). > > Thanks, > Mark. Thanks, Olek