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=-5.1 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,URIBL_BLOCKED,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 6BAF5C4363A for ; Mon, 5 Oct 2020 16:14:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C1A8420756 for ; Mon, 5 Oct 2020 16:14:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="h5hIFeEW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1A8420756 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E8B0F6B008C; Mon, 5 Oct 2020 12:14:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E3B866B0093; Mon, 5 Oct 2020 12:14:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D03126B0095; Mon, 5 Oct 2020 12:14:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0248.hostedemail.com [216.40.44.248]) by kanga.kvack.org (Postfix) with ESMTP id A54AB6B008C for ; Mon, 5 Oct 2020 12:14:20 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 28EB0362C for ; Mon, 5 Oct 2020 16:14:20 +0000 (UTC) X-FDA: 77338369080.14.gold03_630a540271bf Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id 0391D1822987A for ; Mon, 5 Oct 2020 16:14:19 +0000 (UTC) X-HE-Tag: gold03_630a540271bf X-Filterd-Recvd-Size: 4210 Received: from mail-lj1-f196.google.com (mail-lj1-f196.google.com [209.85.208.196]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Mon, 5 Oct 2020 16:14:19 +0000 (UTC) Received: by mail-lj1-f196.google.com with SMTP id l13so4911205ljg.10 for ; Mon, 05 Oct 2020 09:14:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=9E85LeUC9fzbhN9VYe9QKN0L+FRAAc0JnAQy3SaRq1U=; b=h5hIFeEWqehMLSP98uk9ISfHhL6GdIc+qwL/W4YrngM/qqApbLJdUNkf4sYgqGifdK PxUc8fKIGJsB8YchL+lwB1IX+VXMczTYCjzbQBJNG14Kateh/hnmF7+ZxxSt26+McNe5 Gx0FpCcxJknySjfQZHZPyeTCnSRvXsum8wZcQP1/rqgkXIcYEcXKBTNZQDSFkiAUElHx Bb04ZpP9MchbsaUYXuvzoa8AHRvjYfJ1pC6s9PIpK4gmWYNxhEJgYgQOWhmskj/QoFUm OFMu730wmF8ZeCiOkorKnKMF6zFSOfIHMeILWLb+UCE6l7472wV7sEQDG7UuPrYpn7YK EZcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=9E85LeUC9fzbhN9VYe9QKN0L+FRAAc0JnAQy3SaRq1U=; b=t9hVTLEM2YO7iuBvEu1/NSFO4Dn/WGCrH2ATFVoMGLkvhzt78EOTlUQgMsHIKvmC4L GzbPecxW/8EN755AWIcBE4H7oy6ZvtQiha996zJqUxHt7EPjpca1C9oPwwsm+/FR5D0Q twUswS69FFLMv/g/6Hft+Utk7FOJ2qWzqsGkn4PjQ6H4M9K8oqIvs+Vg+Ie1dps++yxi hNv/sEqyY8x9SyrI3TcOIbqUi8LevYALK5iI0HpF/gEO/6X4TMD/ghdNZ50H/wo/+WTg HjIPReCqcD/zMNKFJ4Zujo1kDnIcdRpB680Nv1xBadw7rw/c4OLkUB5iEp+nkfm1OY2E tQEA== X-Gm-Message-State: AOAM5315/yXtQHKE/7S/suZ7OH+fakKpicpAzgOPvZAYnwxpn4Zo3YcF 5plmOChK02UnDvuK8Wfi3oAmMnLqiHE= X-Google-Smtp-Source: ABdhPJyQ/Ie38THkxAFBH0y63mBvh945vThW0vHMrA0RDa4g+2lYSOXp0Up8ocabS9Thu09krQ84lg== X-Received: by 2002:a2e:8904:: with SMTP id d4mr173008lji.322.1601914457962; Mon, 05 Oct 2020 09:14:17 -0700 (PDT) Received: from [192.168.1.97] (88-114-211-119.elisa-laajakaista.fi. [88.114.211.119]) by smtp.gmail.com with ESMTPSA id a25sm50731lfi.267.2020.10.05.09.14.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Oct 2020 09:14:16 -0700 (PDT) Subject: Re: [PATCH] mm: optionally disable brk() To: Jonathan Corbet Cc: Michal Hocko , 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> <2a0f5ade-d770-c36e-50bc-ff0c8e9dacbf@gmail.com> <20201005061248.GN4555@dhcp22.suse.cz> <7d7b1ac5-d6a7-5e43-8fb8-12b844d7f501@gmail.com> <20201005081210.2231e552@lwn.net> From: Topi Miettinen Message-ID: Date: Mon, 5 Oct 2020 19:14:15 +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: <20201005081210.2231e552@lwn.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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 5.10.2020 17.12, Jonathan Corbet wrote: > On Mon, 5 Oct 2020 11:11:35 +0300 > Topi Miettinen wrote: > >> The point is not to shrink the kernel (it will shrink by one small >> function) or get rid of complexity. The point is to disable an inferior >> interface. Memory returned by mmap() is at a random location but with >> brk() it is located near the data segment, so the address is more easily >> predictable. > > So if your true objective is to get glibc to allocate memory differently, > perhaps the right thing to do is to patch glibc? Of course: https://sourceware.org/pipermail/libc-alpha/2020-October/118319.html But since glibc is pretty much the only user of brk(), it also makes sense to disable it in the kernel if nothing uses it anymore. -Topi