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 X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07812C35257 for ; Fri, 2 Oct 2020 21:44:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B78B7206FA for ; Fri, 2 Oct 2020 21:44:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JPuQYQNM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725283AbgJBVoQ (ORCPT ); Fri, 2 Oct 2020 17:44:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725562AbgJBVoO (ORCPT ); Fri, 2 Oct 2020 17:44:14 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D133FC0613D0 for ; Fri, 2 Oct 2020 14:44:13 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id y4so2353213ljk.8 for ; Fri, 02 Oct 2020 14:44:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=eAwV6U5ahvTpKCZ5UaKtD2Y1EcpFb5M2DxULPwBOuyI=; b=JPuQYQNMeiw+8SxbJvN6+HWdt+wRJEnJij4CtnjJ/8uvJ+nmJDXKSMLZJzramQeVzQ dAGsDGUgeTe0NEVzrzje3BEZ+hM2IYlu/HaVrFPH1B5q0Hg3lQfpDhSrlJf0qoOg9tlj ax9bNnNxYpm3kUO/Ii+ybi7WSE5+JnOCWCbygsaI/bkGateA554KGpCuXro18MCogEkx /mwFhVkqpONYbVZ5tPbFtIFsNy2rVDnQ01v+Ue2aDA0neYUMQJufAUi21H5Vv1nzMxpA HvyFyKbackOaob9SbncthU/z2n3XpBTIj/QO1fwJBwYGyqE5hNC4gKve/ls6r6eiQmXm m46w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=eAwV6U5ahvTpKCZ5UaKtD2Y1EcpFb5M2DxULPwBOuyI=; b=VY4cxRNhEqhBk5UF+I5F54Y0s2DGA14QDcDKNK/CbMCdmj2RVkthzGto38MsHz3hPt k1HOckpvw2dFqfED3EEQtSSVidr0G3PrIZGIW33jQmaqMm/OSzevXQjMTg3QJkgbWZEI CPq3bW1vIW5K3snkY2aC9FHaZXrIIFCeZIQCsCVZsIstwk3XlPvfvRwPQaEx6Tf46250 9bS1RKirhRlrg0tBwP7a9MV3wUSXrlK4oxwnamMzQkCy7jGJqxdwqysXydTfxLQXf5nY LgBjOYfYr8eShHee2oM8emrnEgE/DXuVt8Dbr/MeoWTtt20mgZFaeXirqODx8VGLts4j SiZg== X-Gm-Message-State: AOAM530mnmjok8OqdGctNRqhrlKGJcYUBBWh3AJg342tbQWAoCVVqwZR qv9HaUIVMyRGzbi3K2lLGANUZ2nYcUc= X-Google-Smtp-Source: ABdhPJxqTwlMlspJkUUgaH3YRy2gqtqnVmBlHyaYL3jmMJeGgFhH5qP3DHWF51cuFRKzly+l7XhNgg== X-Received: by 2002:a05:651c:102a:: with SMTP id w10mr1221540ljm.64.1601675051875; Fri, 02 Oct 2020 14:44:11 -0700 (PDT) Received: from [192.168.1.84] (88-114-211-119.elisa-laajakaista.fi. [88.114.211.119]) by smtp.gmail.com with ESMTPSA id m1sm667520lfr.32.2020.10.02.14.44.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Oct 2020 14:44:11 -0700 (PDT) Subject: Re: [PATCH] mm: optionally disable brk() To: David Hildenbrand , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20201002171921.3053-1-toiwoton@gmail.com> <653873ef-2a57-37e0-1ac3-fba763652b35@redhat.com> From: Topi Miettinen Message-ID: <2a0f5ade-d770-c36e-50bc-ff0c8e9dacbf@gmail.com> Date: Sat, 3 Oct 2020 00:44:09 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <653873ef-2a57-37e0-1ac3-fba763652b35@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2.10.2020 20.52, David Hildenbrand wrote: > On 02.10.20 19:19, Topi Miettinen wrote: >> The brk() system call allows to change data segment size (heap). This >> is mainly used by glibc for memory allocation, but it can use mmap() >> and that results in more randomized memory mappings since the heap is >> always located at fixed offset to program while mmap()ed memory is >> randomized. > > Want to take more Unix out of Linux? > > Honestly, why care about disabling? User space can happily use mmap() if > it prefers. brk() interface doesn't seem to be used much and glibc is happy to switch to mmap() if brk() fails, so why not allow disabling it optionally? If you don't care to disable, don't do it and this is even the default. -Topi