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[139.178.88.99]) by mx.google.com with ESMTPS id cl5-20020a056a02098500b005cda8ffabb8si3254928pgb.467.2023.12.22.01.14.31 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Dec 2023 01:14:31 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-9535-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99; Authentication-Results: mx.google.com; dkim=pass header.i=@gmx.de header.s=s31663417 header.b=JqZHi07B; spf=pass (google.com: domain of linux-kernel+bounces-9535-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) smtp.mailfrom="linux-kernel+bounces-9535-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=gmx.de Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id D1D61281B80 for ; Fri, 22 Dec 2023 09:14:03 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1C83EDF56; Fri, 22 Dec 2023 09:13:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmx.de header.i=deller@gmx.de header.b="JqZHi07B" X-Original-To: linux-kernel@vger.kernel.org Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 16338D50B; Fri, 22 Dec 2023 09:13:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmx.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1703236424; x=1703841224; i=deller@gmx.de; bh=n+MfHC35t0Y8oIxZ/m3u33zRT3uWWgpuiarIUZkHvsY=; h=X-UI-Sender-Class:Date:Subject:To:Cc:References:From: In-Reply-To; b=JqZHi07BGLzBH6wGJMAtfdqGkRhT4R3mGvXPEuU7a0Ewp4yAVeflRDQ3MdEF7nTY h6TKNHykr+MYBg+DfyomXVyTORB0f74N/lkKcXw336K9LCI5yuYsCy9oMxv7jflmL 7XIC0tfqP8V/DEYw0g8SFy8eVfdmepQgVv1T1Lef22dKthiiVeC7NCZ/yVKzlX4B5 Sjp5a6xXCMQun65pblV6nr8xy+mhlIu3w915+utWrOxkJNyfwmrmS/3/f2neurkia saDB/GsrQuX7yQK/Yt+dJhiXo/i6nCbvcyeqJaYOz/1zGrK7x3eKVY5xwjS1KH+oU ixHhrfAKQDHv5w6sDw== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [192.168.20.55] ([94.134.157.108]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MD9X9-1rPABl2zLd-009BUo; Fri, 22 Dec 2023 10:13:44 +0100 Message-ID: Date: Fri, 22 Dec 2023 10:13:44 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] Section alignment issues? Content-Language: en-US To: Luis Chamberlain , deller@kernel.org Cc: linux-kernel@vger.kernel.org, Masahiro Yamada , Arnd Bergmann , linux-modules@vger.kernel.org, linux-arch@vger.kernel.org References: <20231122221814.139916-1-deller@kernel.org> From: Helge Deller Autocrypt: addr=deller@gmx.de; keydata= xsFNBF3Ia3MBEAD3nmWzMgQByYAWnb9cNqspnkb2GLVKzhoH2QD4eRpyDLA/3smlClbeKkWT HLnjgkbPFDmcmCz5V0Wv1mKYRClAHPCIBIJgyICqqUZo2qGmKstUx3pFAiztlXBANpRECgwJ r+8w6mkccOM9GhoPU0vMaD/UVJcJQzvrxVHO8EHS36aUkjKd6cOpdVbCt3qx8cEhCmaFEO6u CL+k5AZQoABbFQEBocZE1/lSYzaHkcHrjn4cQjc3CffXnUVYwlo8EYOtAHgMDC39s9a7S90L 69l6G73lYBD/Br5lnDPlG6dKfGFZZpQ1h8/x+Qz366Ojfq9MuuRJg7ZQpe6foiOtqwKym/zV dVvSdOOc5sHSpfwu5+BVAAyBd6hw4NddlAQUjHSRs3zJ9OfrEx2d3mIfXZ7+pMhZ7qX0Axlq Lq+B5cfLpzkPAgKn11tfXFxP+hcPHIts0bnDz4EEp+HraW+oRCH2m57Y9zhcJTOJaLw4YpTY GRUlF076vZ2Hz/xMEvIJddRGId7UXZgH9a32NDf+BUjWEZvFt1wFSW1r7zb7oGCwZMy2LI/G aHQv/N0NeFMd28z+deyxd0k1CGefHJuJcOJDVtcE1rGQ43aDhWSpXvXKDj42vFD2We6uIo9D 1VNre2+uAxFzqqf026H6cH8hin9Vnx7p3uq3Dka/Y/qmRFnKVQARAQABzRxIZWxnZSBEZWxs ZXIgPGRlbGxlckBnbXguZGU+wsGRBBMBCAA7AhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheA FiEERUSCKCzZENvvPSX4Pl89BKeiRgMFAl3J1zsCGQEACgkQPl89BKeiRgNK7xAAg6kJTPje uBm9PJTUxXaoaLJFXbYdSPfXhqX/BI9Xi2VzhwC2nSmizdFbeobQBTtRIz5LPhjk95t11q0s uP5htzNISPpwxiYZGKrNnXfcPlziI2bUtlz4ke34cLK6MIl1kbS0/kJBxhiXyvyTWk2JmkMi REjR84lCMAoJd1OM9XGFOg94BT5aLlEKFcld9qj7B4UFpma8RbRUpUWdo0omAEgrnhaKJwV8 qt0ULaF/kyP5qbI8iA2PAvIjq73dA4LNKdMFPG7Rw8yITQ1Vi0DlDgDT2RLvKxEQC0o3C6O4 iQq7qamsThLK0JSDRdLDnq6Phv+Yahd7sDMYuk3gIdoyczRkXzncWAYq7XTWl7nZYBVXG1D8 gkdclsnHzEKpTQIzn/rGyZshsjL4pxVUIpw/vdfx8oNRLKj7iduf11g2kFP71e9v2PP94ik3 Xi9oszP+fP770J0B8QM8w745BrcQm41SsILjArK+5mMHrYhM4ZFN7aipK3UXDNs3vjN+t0zi qErzlrxXtsX4J6nqjs/mF9frVkpv7OTAzj7pjFHv0Bu8pRm4AyW6Y5/H6jOup6nkJdP/AFDu 5ImdlA0jhr3iLk9s9WnjBUHyMYu+HD7qR3yhX6uWxg2oB2FWVMRLXbPEt2hRGq09rVQS7DBy dbZgPwou7pD8MTfQhGmDJFKm2jvOwU0EXchrcwEQAOsDQjdtPeaRt8EP2pc8tG+g9eiiX9Sh rX87SLSeKF6uHpEJ3VbhafIU6A7hy7RcIJnQz0hEUdXjH774B8YD3JKnAtfAyuIU2/rOGa/v UN4BY6U6TVIOv9piVQByBthGQh4YHhePSKtPzK9Pv/6rd8H3IWnJK/dXiUDQllkedrENXrZp eLUjhyp94ooo9XqRl44YqlsrSUh+BzW7wqwfmu26UjmAzIZYVCPCq5IjD96QrhLf6naY6En3 ++tqCAWPkqKvWfRdXPOz4GK08uhcBp3jZHTVkcbo5qahVpv8Y8mzOvSIAxnIjb+cklVxjyY9 dVlrhfKiK5L+zA2fWUreVBqLs1SjfHm5OGuQ2qqzVcMYJGH/uisJn22VXB1c48yYyGv2HUN5 lC1JHQUV9734I5cczA2Gfo27nTHy3zANj4hy+s/q1adzvn7hMokU7OehwKrNXafFfwWVK3OG 1dSjWtgIv5KJi1XZk5TV6JlPZSqj4D8pUwIx3KSp0cD7xTEZATRfc47Yc+cyKcXG034tNEAc xZNTR1kMi9njdxc1wzM9T6pspTtA0vuD3ee94Dg+nDrH1As24uwfFLguiILPzpl0kLaPYYgB wumlL2nGcB6RVRRFMiAS5uOTEk+sJ/tRiQwO3K8vmaECaNJRfJC7weH+jww1Dzo0f1TP6rUa fTBRABEBAAHCwXYEGAEIACAWIQRFRIIoLNkQ2+89Jfg+Xz0Ep6JGAwUCXchrcwIbDAAKCRA+ Xz0Ep6JGAxtdEAC54NQMBwjUNqBNCMsh6WrwQwbg9tkJw718QHPw43gKFSxFIYzdBzD/YMPH l+2fFiefvmI4uNDjlyCITGSM+T6b8cA7YAKvZhzJyJSS7pRzsIKGjhk7zADL1+PJei9p9idy RbmFKo0dAL+ac0t/EZULHGPuIiavWLgwYLVoUEBwz86ZtEtVmDmEsj8ryWw75ZIarNDhV74s BdM2ffUJk3+vWe25BPcJiaZkTuFt+xt2CdbvpZv3IPrEkp9GAKof2hHdFCRKMtgxBo8Kao6p Ws/Vv68FusAi94ySuZT3fp1xGWWf5+1jX4ylC//w0Rj85QihTpA2MylORUNFvH0MRJx4mlFk XN6G+5jIIJhG46LUucQ28+VyEDNcGL3tarnkw8ngEhAbnvMJ2RTx8vGh7PssKaGzAUmNNZiG MB4mPKqvDZ02j1wp7vthQcOEg08z1+XHXb8ZZKST7yTVa5P89JymGE8CBGdQaAXnqYK3/yWf FwRDcGV6nxanxZGKEkSHHOm8jHwvQWvPP73pvuPBEPtKGLzbgd7OOcGZWtq2hNC6cRtsRdDx 4TAGMCz4j238m+2mdbdhRh3iBnWT5yPFfnv/2IjFAk+sdix1Mrr+LIDF++kiekeq0yUpDdc4 ExBy2xf6dd+tuFFBp3/VDN4U0UfG4QJ2fg19zE5Z8dS4jGIbLg== In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:3zEqUv9AZnY9J4XQazbk3elNn/rcWjDfLdQDJzqcBLfiUhtMYSh jJkPybvj/oYwFs6O3Wu2JWJjbAao1IvpGCuWw/TyaDY7OJ3SrocW4QBDZvqOfUawqyVyC5G 1jVQ5lIrsDnFJ/M1maFDa24ThdS27PZxoCjxS/J3oZDpfA2no53glPX21EyY1kk76OiZztP fI9dQ6K324bndN9usJQaA== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:AMQrj8E/jfQ=;E1jhV0dKW144QoERt+ctLefPCuZ cbOmp+8WED+2rLEFeeijZJfwFuWs8BSuDhb0I10/pt9hZJlHcy1NH1ZAnyEvUy245iJ35e5T+ n9l4kNfdKAALewRc1k69ieHMhQ+w2MNHs7xwL1Vs4Nl2QytR6iHTEwx3dFxqzqvDZTSvxUZLF uF0HN4Yyz2esmCZwzzTJ7cyLz6tnP10gezcIRvKXSjYpKD2dVwal8TM2zLFPOQBIFKff/2b9O 4XFCsMCAlNOxslVwQqHt98MD8vK0l9A1QzJxwfqnc2GGsRniicjO6ki6X+8in+uJPPC96XtkB J9C8EL+mWpMFU+D8eLJJ8kI34rnrRuwuCtS7CqoSRP4NnI3YGKGLm8p4FN86Ir4Ijth3eQrH/ 2iyBGdl6vWcutoXVQ1k5jT1gju6TBFk0aU6U17SOamK7++SVq3wvArCOls8wNHH9PB4Ah7gNT YapJqaM/vYGVIH+3LS94i6UTfrueEcNDwKuLdRKfTTCR/JpW8xhV9SJN4o1iWElEhIci+/ptw bVm/64tb87Ps2aWjd4fFVyQWHwrFAoRAwB9KhI/MmWJpkpwoxqLQ6sY6I2mrmNObNIY9ZoQ85 7clab0kdwmkxNsdLgsrVn4RHr0z4UyXln/948KX9HfUB98HlHNZvMhXcEj0H4KVJN9oYWAZgA 3ZNyTg3yGMxe6MacJbq1E6awRZXGbLNEcLVKZSssuhm8Z43IoB7J+cVMH9Ec8Hiy7GuYyNNnJ iWZVGZuCfE2vdm0Gw/z9/pnfb5x8Qa9P0wLSEPqGggT4Xv/n4zCImMuuTiwXtFKzyw6dCtM6h CEE2SIzASJiirCnWI2IM1zJQtg5Dzhh5r5UIm+6i/s/ZLX5jL2V04PvpuB9GrgdFnXE1mEkMD g005RLUKxnJQ2Xb7A1YPIzUBp9VYaMYb8DThOIye/4NAgYptq5gMJlfMmS4FzOkpwZcs2SoPm D4pB7QmUCfkXlgVlcNG0devB9LI= On 12/20/23 20:40, Luis Chamberlain wrote: > On Tue, Dec 19, 2023 at 01:26:49PM -0800, Luis Chamberlain wrote: >> On Wed, Nov 22, 2023 at 11:18:10PM +0100, deller@kernel.org wrote: >>> From: Helge Deller >>> My questions: >>> - Am I wrong with my analysis? >> >> This would typically of course depend on the arch, but whether it helps >> is what I would like to see with real numbers rather then speculation. >> Howeer, I don't expect some of these are hot paths except maybe the >> table lookups. So could you look at some perf stat differences >> without / with alignment ? Other than bootup live patching would be >> a good test case. We have selftest for modules, the script in selftests >> tools/testing/selftests/kmod/kmod.sh is pretty aggressive, but the live >> patching tests might be better suited. >> >>> - What does people see on other architectures? >>> - Does it make sense to add a compile- and runtime-check, like the pat= ch below, to the kernel? >> >> The chatty aspects really depend on the above results. >> >> Aren't there some archs where an unaligned access would actually crash? >> Why hasn't that happened? > > I've gone down through memory lane and we have discussed this before. > > It would seem this misalignment should not affect performance, and this > should not be an issue unless you have a buggy exception hanlder. We > actually ran into one before. Please refer to merge commit > > e74acdf55da6649dd30be5b621a93b71cbe7f3f9 Yes, this is the second time I stumbled over this issue. But let's continue discussing in the other mail thread... Helge