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[2003:d8:2f44:9200:3344:447e:353c:bf0b]) by smtp.gmail.com with ESMTPSA id l22sm3203749wmp.34.2021.12.03.10.20.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Dec 2021 10:20:46 -0800 (PST) Message-ID: <1e0ce8f6-332b-399f-5ac7-5a56639172b3@redhat.com> Date: Fri, 3 Dec 2021 19:20:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [RFD] clear virtual machine memory when virtual machine is turned off To: Mike Kravetz , fei luo , akpm@linux-foundation.org, arnd@arndb.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org Cc: Joao Martins References: <673c5628-da97-83d3-028f-46219f203caf@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: ACDB9B000093 X-Stat-Signature: ued9mx4s41ngbbp89qtysbyg7waidgz5 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bhHBJvxi; spf=none (imf19.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1638555649-115150 Content-Transfer-Encoding: quoted-printable 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 02.12.21 18:27, Mike Kravetz wrote: > On 12/2/21 04:47, David Hildenbrand wrote: >> On 02.12.21 11:19, fei luo wrote: >>> >>> When reusing the page that has been cleared, there is no need to clea= r it >>> >>> again,=C2=A0which also speeds up the memory allocation of user-mode p= rograms. >>> >>> >>> Is this feature feasible? >> >> "init_on_free=3D1" for the system as a whole, which might sounds like = what >> might tackle part of your use case. >> >=20 > Certainly init_on_free will not make much difference if VMs are backed = by > hugetlb pages. We (Joao and myself) have thought about clearing hugetl= b > pages from user space in an attempt speed up launching of VMs backed by > hugetlb pages. >=20 I remember that discussion. And I also recall a discussion regarding extending init_on_free semantics to hugetlbfs. --=20 Thanks, David / dhildenb