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Thu, 03 Sep 2020 14:09:16 -0400 X-MC-Unique: ybdrIaCtPOGHbgOcG5PVqQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 47D6A807346; Thu, 3 Sep 2020 18:09:14 +0000 (UTC) Received: from [10.36.112.104] (ovpn-112-104.ams2.redhat.com [10.36.112.104]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9D8375D9CC; Thu, 3 Sep 2020 18:09:10 +0000 (UTC) Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller To: Pavel Tatashin , Michal Hocko Cc: David Hildenbrand , Vlastimil Babka , Roman Gushchin , Bharata B Rao , "linux-mm@kvack.org" , Andrew Morton , Johannes Weiner , Shakeel Butt , Vladimir Davydov , "linux-kernel@vger.kernel.org" , Kernel Team , Yafang Shao , stable , Linus Torvalds , Sasha Levin , Greg Kroah-Hartman References: <6469324e-afa2-18b4-81fb-9e96466c1bf3@suse.cz> <20200902135018.GF4617@dhcp22.suse.cz> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Rspamd-Queue-Id: 5D0791800DC8D X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: > For performance reasons during system updates/reboots we do not erase > memory content. The memory content is erased only on power cycle, > which we do not do in production. > > Once we hot-remove the memory, we convert it back into DAXFS PMEM > device, format it into EXT4, mount it as DAX file system, and allow > programs to serialize their states to it so they can read it back > after the reboot. > > During startup we mount pmem, programs read the state back, and after > that we hotplug the PMEM DAX as a movable zone. This way during normal > runtime we have 8G available to programs. > Thanks for sharing the workflow - while it sounds somewhat sub-optimal, I guess it gets the job done using existing tools / mechanisms. (I remember the persistent tmpfs over kexec RFC, which tries to tackle it by introducing something new) -- Thanks, David / dhildenb