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 CBB42D339AE for ; Mon, 28 Oct 2024 18:24:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 24BD46B0098; Mon, 28 Oct 2024 14:24:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1FA326B0099; Mon, 28 Oct 2024 14:24:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0748E6B009A; Mon, 28 Oct 2024 14:24:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id D95A76B0098 for ; Mon, 28 Oct 2024 14:24:20 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 5EDCAC0707 for ; Mon, 28 Oct 2024 18:24:20 +0000 (UTC) X-FDA: 82723834704.07.78F339F Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf25.hostedemail.com (Postfix) with ESMTP id E321EA0028 for ; Mon, 28 Oct 2024 18:24:01 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fCSmkWVX; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf25.hostedemail.com: domain of sj@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=sj@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1730139684; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=geDkZvM8HCGgfUx3GpLB/r0wTZt8/03ec8Gk5wNZTXk=; b=r9pDJ84j2F1HGsWqS9QW1ZaV57TEy0uqOS4+s2fb7aWVfYAEG/i+TF/NLAu/7gFmAq+WQV cV9XIyfimG5nfZFRLRZV6PizmmuHRvXRfNG6Snofkspci2FaMBXLAkiMot4BNAHOxnRK+q ssG5TAcs6JCT2vWF+UnO4xyiJ0c2W1w= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1730139684; a=rsa-sha256; cv=none; b=jshwhibXCqLpDPOQ9X3ZtZYBP81AKgkh/d6jqI53l6+OaaDwhS7oS22HVZhIHYkHnVZfnz 2xW62hC6FSzGMIWzMC52Or+Wms9Gk3hVhCk8YJ4lHTN+rijjwGJFDRxmJkPlaa5DtK6g6q 6UWD6LWIiKKQWsZTSYer+0CnAIycFFU= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=fCSmkWVX; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf25.hostedemail.com: domain of sj@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=sj@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id A238CA42AB6; Mon, 28 Oct 2024 18:22:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8ED80C4CEC3; Mon, 28 Oct 2024 18:24:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730139856; bh=Dc2nfSd4gFZOOCQf51oe06WNS9JqcUB5O926K4UYWDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fCSmkWVXt9faMdPUgXr92nQ0Nd+XrerOUvEAhYwHTcr8MRTGylHk4evQh0xHDRjOX SHVZXpDvpxMwMX1M1S5R7Mdl7i5yr7w0C6uCUy+T9SVAGQ5BehH1B7l7Hnruer33ig p0sJd+xHOBlqZMRs2YpfF5WM6IfCsSIA/TUyEeO2krcDFVBqY4nfnwFAym5yoSjiLz RGP/fgh65ns9VVUCARVqDVtrI/Rg4Y4Tt7vkcyhP09vktn9UQGOBLPLFDEdUFrb+1F qTrMZAjZ99HRgBSdsuah6pOGrpsvrP/eiZwYjozx98DtLytURMVqye2eAQ+MZHtCIg opA8bKnAsUR8w== From: SeongJae Park To: Lorenzo Stoakes Cc: SeongJae Park , Andrew Morton , "Liam R . Howlett" , Matthew Wilcox , Vlastimil Babka , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , linux-api@vger.kernel.org, John Hubbard Subject: Re: [PATCH v4 0/5] implement lightweight guard pages Date: Mon, 28 Oct 2024 11:24:13 -0700 Message-Id: <20241028182413.277218-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E321EA0028 X-Stat-Signature: jaadysagti1gwmbqxwxnxpkwsseqgefe X-Rspam-User: X-HE-Tag: 1730139841-68276 X-HE-Meta: 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 nTfaOhfa KU61gqEoaxYyp6VUH6+X8s4q7VzEOcF4bvp21Sf2TOMmT/9/rV/OYK43XK75EdhhQL8kfGLsCQMrTNDGu5SwS9vdnCj7i9ol3sr0qpbucceG0QiAJCvEoRlbGFMvYZjoxLvxYhVBcGeXbRtS52XpaJstVQu4Q+SmZmdZw67/VsebBde+yI9+Gntaj2/78u150EsUPifOeafLaxGB2TSaxppCLAQ== 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: List-Subscribe: List-Unsubscribe: On Mon, 28 Oct 2024 14:13:26 +0000 Lorenzo Stoakes wrote: > Userland library functions such as allocators and threading implementations > often require regions of memory to act as 'guard pages' - mappings which, > when accessed, result in a fatal signal being sent to the accessing > process. > > The current means by which these are implemented is via a PROT_NONE mmap() > mapping, which provides the required semantics however incur an overhead of > a VMA for each such region. > > With a great many processes and threads, this can rapidly add up and incur > a significant memory penalty. It also has the added problem of preventing > merges that might otherwise be permitted. > > This series takes a different approach - an idea suggested by Vlasimil > Babka (and before him David Hildenbrand and Jann Horn - perhaps more - the Nit. s/Vlasimil/Vlastimil/ ;) Thanks, SJ [...]