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[201.92.249.168]) by smtp.gmail.com with ESMTPSA id h10sm11260478qtk.18.2019.10.15.06.58.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Oct 2019 06:58:40 -0700 (PDT) Subject: Re: [PATCH] hugetlb: Add nohugepages parameter to prevent hugepages creation To: Michal Hocko , Guilherme Piccoli Cc: Qian Cai , linux-mm@kvack.org, mike.kravetz@oracle.com, linux-kernel@vger.kernel.org, Jay Vosburgh , "Guilherme G. Piccoli" References: <4641B95A-6DD8-4E8A-AD53-06E7B72D956C@lca.pw> <20191015121803.GB24932@dhcp22.suse.cz> From: "Guilherme G. Piccoli" Message-ID: Date: Tue, 15 Oct 2019 10:58:36 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191015121803.GB24932@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.198224, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/15/19 9:18 AM, Michal Hocko wrote: > I do agree with Qian Cai here. Kdump kernel requires a very tailored > environment considering it is running in a very restricted > configuration. The hugetlb pre-allocation sounds like a tooling problem > and should be fixed at that layer. > Hi Michal, thanks for your response. Can you suggest me a current way of preventing hugepages for being created, using userspace? The goal for this patch is exactly this, introduce such a way. As I've said before, Ubuntu kdump rely on rootfs mounting and there's no official statement or documentation that say it's wrong to do this way - although I agree initrd-only approach is more safe. But since Ubuntu kdump rely on rootfs mount, we couldn't find a way to effectively prevent the creation of hugepages completely, hence we tried to introduce one. Cheers, Guilherme