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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pmca4-006zfX-GL; Wed, 12 Apr 2023 15:40:20 +0000 Date: Wed, 12 Apr 2023 16:40:20 +0100 From: Matthew Wilcox To: Kyungsan Kim Cc: david@redhat.com, lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-cxl@vger.kernel.org, a.manzanares@samsung.com, viacheslav.dubeyko@bytedance.com, dan.j.williams@intel.com, seungjun.ha@samsung.com, wj28.lee@samsung.com Subject: Re: FW: [LSF/MM/BPF TOPIC] BoF VM live migration over CXL memory Message-ID: References: <20230412111033.434644-1-ks0204.kim@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230412111033.434644-1-ks0204.kim@samsung.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BD2571A0006 X-Stat-Signature: o3obpa1taig5hh8ysqjjnayddykjfucu X-Rspam-User: X-HE-Tag: 1681314036-793375 X-HE-Meta: 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 0+q1jUzW 8aYAp2KgEwSaEgGfoV/nsAsh1DlJIEH2RrmN7u0+pgvu7rbN7DEMtohYemcKJi0E3wWr74pDbf1GbIkrccWWcJQhs8LUvQx5q5EZi0MA/jivEptkaDNzgA5n8nNMYqZSJ72yz24jCIqqXqYpT0040Nje5yUeKGVtA1Z3JAxIWkbya4ZSt84I9z8tEYg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.004902, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 12, 2023 at 08:10:33PM +0900, Kyungsan Kim wrote: > Pinning and plubbability is mutual exclusive so it can not happen at the same time. > What we argue is ZONE_EXMEM does not "confine movability". an allocation context can determine the movability attribute. > Even one unmovable allocation will make the entire CXL DRAM unpluggable. > When you see ZONE_EXMEM just on movable/unmoable aspect, we think it is the same with ZONE_NORMAL, > but ZONE_EXMEM works on an extended memory, as of now CXL DRAM. > > Then why ZONE_EXMEM is, ZONE_EXMEM considers not only the pluggability aspect, but CXL identifier for user/kenelspace API, > the abstraction of multiple CXL DRAM channels, and zone unit algorithm for CXL HW characteristics. > The last one is potential at the moment, though. > > As mentioned in ZONE_EXMEM thread, we are preparing slides to explain experiences and proposals. > It it not final version now[1]. > [1] https://github.com/OpenMPDK/SMDK/wiki/93.-%5BLSF-MM-BPF-TOPIC%5D-SMDK-inspired-MM-changes-for-CXL The problem is that you're starting out with a solution. Tell us what your requirements are, at a really high level, then walk us through why ZONE_EXMEM is the best way to satisfy those requirements. Also, those slides are terrible. Even at 200% zoom, the text is tiny. There is no MAP_NORMAL argument to mmap(), there are no GFP flags to sys_mmap() and calling mmap() does not typically cause alloc_page() to be called. I'm not sure that putting your thoughts onto slides is making them any better organised.