From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-4.7 required=5.0 tests=DKIM_ADSP_ALL,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id C8A827D089 for ; Tue, 13 Nov 2018 14:23:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730998AbeKNAWP (ORCPT ); Tue, 13 Nov 2018 19:22:15 -0500 Received: from vulcan.natalenko.name ([104.207.131.136]:57040 "EHLO vulcan.natalenko.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726846AbeKNAWP (ORCPT ); Tue, 13 Nov 2018 19:22:15 -0500 Received: from mail.natalenko.name (vulcan.natalenko.name [IPv6:fe80::5400:ff:fe0c:dfa0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by vulcan.natalenko.name (Postfix) with ESMTPSA id 8928E46A727; Tue, 13 Nov 2018 15:23:50 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=natalenko.name; s=dkim-20170712; t=1542119030; 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:content-transfer-encoding: in-reply-to:in-reply-to:references; bh=wgm6gey+f3ws2zmlqkX9o3gU/iYvoQHfgHIV4E13ko0=; b=ox0hDIYkv1p2Fjq/Hm9CqCagXiXractkZLTORRvRYjcqtA1Amcptu5Q0VdH4EdMegWcvfT +LZ0xndurYypujVSk0cQpymoKrOcDRNksPu6nT6YN9vph/E82wh/jINPxYnhHB7iWKX79e l36QWE8k7+pohYri6ktYaDiHnDqGr0I= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 13 Nov 2018 15:23:50 +0100 From: Oleksandr Natalenko To: jannh@google.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, timofey.titovets@synesis.ru, willy@infradead.org Subject: Re: [PATCH V3] KSM: allow dedup all tasks memory In-Reply-To: <> Message-ID: X-Sender: oleksandr@natalenko.name User-Agent: Roundcube Webmail/1.3.8 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=natalenko.name; s=arc-20170712; t=1542119030; 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:content-transfer-encoding: in-reply-to:in-reply-to:references; bh=wgm6gey+f3ws2zmlqkX9o3gU/iYvoQHfgHIV4E13ko0=; b=EfMsPh0t52POejsE3ot0hiCoUH/comDhm2b/LZ3pqbKvBM6iBCRggPHR16pF4xh/Sfz8zA IoWpAGGYmG/eISPiGzogiP6resYwclssTA+YUnjkYRapXe+P09woRG5tQsNNjtRz3+j+TC 5V43EVczPDZ6TMjsd7vKfaI32530EDE= ARC-Seal: i=1; s=arc-20170712; d=natalenko.name; t=1542119030; a=rsa-sha256; cv=none; b=Sj/SZEixUX1evZEiMY5cVPmGNs0HJkekyzpaftizq64/M97myapUcxz6gdpSN5XJ/idX/HPIi7G2CTrR1G4UeyDmLoKA6r3bX7A3l8wHfx9UMALynzlrK0G3FdoKWAB/8GUSfR8IbuRAmgu5+lB61Ur6ROnfIooaVhCbitCq3UA= ARC-Authentication-Results: i=1; vulcan.natalenko.name; auth=pass smtp.auth=oleksandr@natalenko.name smtp.mailfrom=oleksandr@natalenko.name Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi. > Yep. However, so far, it requires an application to explicitly opt in > to this behavior, so it's not all that bad. Your patch would remove > the requirement for application opt-in, which, in my opinion, makes > this way worse and reduces the number of applications for which this > is acceptable. The default is to maintain the old behaviour, so unless the explicit decision is made by the administrator, no extra risk is imposed. > As far as I know, basically nobody is using KSM at this point. There > are blog posts from several cloud providers about these security risks > that explicitly state that they're not using memory deduplication. I tend to disagree here. Based on both what my company does and what UKSM users do, memory dedup is a desired option (note "option" word here, not the default choice). Thanks. -- Oleksandr Natalenko (post-factum)