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[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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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