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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10DDEC77B77 for ; Mon, 17 Apr 2023 06:05:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1F03B8E0002; Mon, 17 Apr 2023 02:05:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 19EB38E0001; Mon, 17 Apr 2023 02:05:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 066A28E0002; Mon, 17 Apr 2023 02:05:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id EBA2A8E0001 for ; Mon, 17 Apr 2023 02:05:37 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id B1F8980396 for ; Mon, 17 Apr 2023 06:05:37 +0000 (UTC) X-FDA: 80689846314.01.164C77F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf18.hostedemail.com (Postfix) with ESMTP id EB4481C0013 for ; Mon, 17 Apr 2023 06:05:35 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=linuxfoundation.org header.s=korg header.b=NaVp702n; spf=pass (imf18.hostedemail.com: domain of gregkh@linuxfoundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org; dmarc=pass (policy=none) header.from=linuxfoundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1681711536; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1X3FaLxoC+1cMTQm4sacczuNW4TScHumtekE+FtOX18=; b=fUzOHYVU43iSNEh5OfKCstTcdmWR1zxRBCcw1XnKbX4eMrFL7l7fIFYGLynfAYCjMco3LW k2LjKQfpViO7HYAY8PPMaZ1BkDyY6yvg9HTJwol2jaEjv0ouLRy6lkkuWtYjVQGooE9d45 fZzwvBHCd2EblrwZ5W+Lz1w9zGbQI9A= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=linuxfoundation.org header.s=korg header.b=NaVp702n; spf=pass (imf18.hostedemail.com: domain of gregkh@linuxfoundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org; dmarc=pass (policy=none) header.from=linuxfoundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1681711536; a=rsa-sha256; cv=none; b=GU7npFTjsSWWGHXSjbEDJnM+DGaLykcmTygnmoStzPJK8qHDkGuMWpb9w1M7D5kLYGMZTt AVg+YfiqiLGh6XB/xoL8TA7bSMM/iIaTvfVhBhXplIGtd0WEE3Xl2oR6VCQLmiiJBXNYgm 5KhxNiVhW4TSb7ntDSHAaQnlyTXf7qE= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E4C6E60B54; Mon, 17 Apr 2023 06:05:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0DCDC433D2; Mon, 17 Apr 2023 06:05:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1681711534; bh=NwGailapraVjI3JxBj0hy2nPk+sbOBpvNBegUBFYK60=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NaVp702ncCjgvIBQuBUWkcim7cOoz9Cwe0ShV77d9SaBO8XpvXvpMCnZPzCqbX7/h craG63gOX8mL5t6mVrSxVDRLyqNvD23VPPqXzDs3S9SVnNWbD6L65Yz2uKJGbut4RU F/l9kAWcIA2TQO429FaSTKVa8ffpaWZo68MT8GkU= Date: Mon, 17 Apr 2023 08:05:31 +0200 From: Greg KH To: Luis Chamberlain Cc: Christoph Hellwig , Kees Cook , david@redhat.com, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, pmladek@suse.com, petr.pavlu@suse.com, prarit@redhat.com, torvalds@linux-foundation.org, rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de, peterz@infradead.org, song@kernel.org, rppt@kernel.org, dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com, colin.i.king@gmail.com, jim.cromie@gmail.com, catalin.marinas@arm.com, jbaron@akamai.com, rick.p.edgecombe@intel.com Subject: Re: [RFC 2/2] kread: avoid duplicates Message-ID: References: <20230414052840.1994456-1-mcgrof@kernel.org> <20230414052840.1994456-3-mcgrof@kernel.org> <2023041637-glamorous-appetite-dc12@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EB4481C0013 X-Rspam-User: X-Stat-Signature: kdcttihiw7j958hza85wn53oszfa1g17 X-HE-Tag: 1681711535-783583 X-HE-Meta: U2FsdGVkX19j8tBgzvj9XlpZbdCHUX2Q/I09vUuYTNZi6P2SMGOTA53dK7UMKfPxeg6qPXxqVPuTVTMBoKdtFzACYsxD29MEUVoe5YS5S64FJ8nSBEmPRbTVduWJZ5JZ0/g/5vc58iIrhHhwaO4lkf+lcL6NCiION5Lgg5rOWp1wYofUFg3mrd8Qh/GAVas8w5bt4aC7NHcYV0uBwLf0l8uFF3aGqR/yqtXHTD05DnG1P56lna72inYiS0WG1u2+MJlhu18LjDS36p7dMQktYSE89YleNPD/4rb5rnnt7/3hCC5uxU7+1lbUBWpzwUtmlPMSZfwuWHMSIwP4/EjiH2t0xD0qR7OJObcDhaR/URdxa6Cw7FE5WvVojTd0VpOCtiYVm0pU2SDxyWd62EfODRAllPJwZ7mmSNBx85qZs+PNTOd6IpoFDw4nje82lL1MAdVzJuCnTBzO78jjvVeBc2KEy6k0h8wdjaPVkNBT4ylJNxV63Mqw5E8UMKXScFkasv1HaDJdqA+06tDXxtKJGTi8sH8xkfYCzVCziaLHFh5hLZch1M7E9YAf8EmBL8mCFBnBcXFkXWUTefr+WIUrkPf7sjX98ywORBlexIjUKGI6AFxgfuGGRuiIbkKDKDT/WStXSUoN0uPGEyDYhKoEdfQ4d5t5LjBA2BelHMOWOCsw0G48zviyb1xsQzVCIapDj7d8fmGdrK8M1vitv6JjM+J6UZNujEaze6St5/FHYm+zUMK574VeNbdQP7OC41Nna0UuFTfhW75J8sPr333R/OjgH4yBOMkVnppa8wVJ8ZxIcBsLXmMn63oJ8PZfQQ6VhKIZ1UgihxHKItmtcMduVLwIEIS+5uhjk4SJP+ey8thXi7+60Lm6xTubKRubCBPZkH3ooULhYse5BPCtfSKYv3zFNviCuQ4ZxoGJltGltWgreDbEiLIbOm6ht+QR1QTo8Zp0gJRqxnP8J2qpIHc wLxNBpal gthX4B2vdOt1dycF6M8/wPXA8obzf1d/XQwzky/FO+O0Qs9QSxsKTlUOCy6Ci0rjYvKBKOsETFcrUENov0bA8E1YW68DBOXa5VztQzvXV8GxBotU8NA0CTsSkzomPXrbA6TVukb+FReAzZmiYh/6dOqUdYD+uryey4tASs37CoJZhxbInvB1+gaRCKSfCXbvWMnZmYekETN7Fk3gTNfneHWVDPtVBze5UxItrCq2WwRo6SOQjjuCcxgSwxihJdScvHLddGaRWRb3XXpDQCtwUv6wrxOGofKCel//k65/jdDaWjIVbMYJmhJXzw/pKLGfjnv9cbQncTUmJJHGCopDbTN7W5vYx+RvM0V4IvtMtb5r0khE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Apr 16, 2023 at 11:46:44AM -0700, Luis Chamberlain wrote: > On Sun, Apr 16, 2023 at 02:50:01PM +0200, Greg KH wrote: > > On Sat, Apr 15, 2023 at 11:41:28PM -0700, Luis Chamberlain wrote: > > > On Sat, Apr 15, 2023 at 11:04:12PM -0700, Christoph Hellwig wrote: > > > > On Thu, Apr 13, 2023 at 10:28:40PM -0700, Luis Chamberlain wrote: > > > > > With this we run into 0 wasted virtual memory bytes. > > > > > > > > Avoid what duplicates? > > > > > > David Hildenbrand had reported that with over 400 CPUs vmap space > > > runs out and it seems it was related to module loading. I took a > > > look and confirmed it. Module loading ends up requiring in the > > > worst case 3 vmalloc allocations, so typically at least twice > > > the size of the module size and in the worst case just add > > > the decompressed module size: > > > > > > a) initial kernel_read*() call > > > b) optional module decompression > > > c) the actual module data copy we will keep > > > > > > Duplicate module requests that come from userspace end up being thrown > > > in the trash bin, as only one module will be allocated. Although there > > > are checks for a module prior to requesting a module udev still doesn't > > > do the best of a job to avoid that and so we end up with tons of > > > duplicate module requests. We're talking about gigabytes of vmalloc > > > bytes just lost because of this for large systems and megabytes for > > > average systems. So for example with just 255 CPUs we can loose about > > > 13.58 GiB, and for 8 CPUs about 226.53 MiB. > > > > How does the memory get "lost"? Shouldn't it be properly freed when the > > duplicate module load fails? > > Yes memory gets freed, but since virtual memory space can be limitted it > also means you can end up eventually getting to the point -ENOMEMs will > happen as you have more CPUS and you cannot use virtual memory for other > things during kernel bootup and bootup fails. This is apparently > exacerbated with KASAN enabled. Then why not just rate-limit the module loader in userspace on such large systems if that's an issue? No kernel changes needed to do that. thanks, greg k-h