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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1piEGZ-00BQpk-1x; Fri, 31 Mar 2023 12:54:03 +0000 Date: Fri, 31 Mar 2023 13:54:03 +0100 From: Matthew Wilcox To: Kyungsan Kim Cc: 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: Re: RE(2): FW: [LSF/MM/BPF TOPIC] SMDK inspired MM changes for CXL Message-ID: References: <20230331113715.400135-1-ks0204.kim@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230331113715.400135-1-ks0204.kim@samsung.com> X-Rspam-User: X-Rspamd-Queue-Id: 3F6B54001C X-Rspamd-Server: rspam01 X-Stat-Signature: ah1mjcppy9ucaco9twjagzfyii8aujw5 X-HE-Tag: 1680267254-735217 X-HE-Meta: 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 IdfEmP+U Z8PpgxBE7kaIhFQm7ZJh9kh9bArxeIo73AmObJAlFT3qyvd3aSC2yZc+UazTiUeb7R07FJ26DGdyZmxmUXcK52PoXWT1QS2h39uRTzvTFpaAq9uTH590vaWZo4bToKImfDYX9G720Q7CEq9SsG4VeFDdaIkLJvSzep8RlgzRn+I6RUM6kUfKf9++uDge//f7XpahpBtbosFARUNU14e4fjz/ZMg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000297, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Mar 31, 2023 at 08:37:15PM +0900, Kyungsan Kim wrote: > >> We resolved the issue using ZONE_EXMEM by allowing seletively choice of the two usecases. > > > >This sounds dangerously confused. Do you want the EXMEM to be removable > >or not? If you do, then allocations from it have to be movable. If > >you don't, why go to all this trouble? > > I'm sorry to make you confused. We will try more to clearly explain our thought. > We think the CXL DRAM device should be removable along with HW pluggable nature. > For MM point of view, we think a page of CXL DRAM can be both movable and unmovable. > An user or kernel context should be able to determine it. Thus, we think dedication on the ZONE_NORMAL or the ZONE_MOVABLE is not enough. No, this is not the right approach. If CXL is to be hot-pluggable, then all CXL allocations must be movable. If even one allocation on a device is not movable, then the device cannot be removed. ZONE_EXMEM feels like a solution in search of a problem.