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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c0a852b95fsm162892085a.116.2025.02.18.10.04.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Feb 2025 10:04:52 -0800 (PST) Date: Tue, 18 Feb 2025 13:04:50 -0500 From: Gregory Price To: Yang Shi Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: CXL Boot to Bash - Section 3: Memory (block) Hotplug Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 24C794002F X-Stat-Signature: 4793txs8mfgtgdxuz9iq8wzwnpo81mbq X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1739901893-979928 X-HE-Meta: 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 IjuJMaVp prcEUUx0vUwGEGmiW3F2ilwZqSHiqgiSpL7q6Ux2oCWtbhOLlg12fR2ZHdBYdi1z6/k0VU6jXUTJb+WFo9Jpxqwew1aELzS8vXrIYZTkg6wzLBKkWtl9w7migJf6u6ctUh3C2VAA7Ex/SBO/99cqgGsffSt6hvKrfGmnu4scygrSQ3/mJC7kZvdjbwhRhBsqe6ax9qKzw+1pwcSEN6ZkNDT8U6jqiyWIQl6D64gjLbMNfYLWsAdjSDaDEFAbLAWGZ02e6z9ddshVAyI7yiKep6m3pj6QrllQuo24BbC+KDmjlBPBEPrVY8HPnYJU380c0Mwq0oBgA83ga+hiugyaQudHQDxyr5Z6NkMmFQW5WbQ9cBmDhTEJKGhAjxJCkwtAfLz5dDTpBAvcHEVH2M4v/JA3QdOKp9omwchqs X-Bogosity: Ham, tests=bogofilter, spamicity=0.000997, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 18, 2025 at 09:49:28AM -0800, Yang Shi wrote: > On Mon, Feb 17, 2025 at 12:05 PM Gregory Price wrote: > > The node ID passed in as an argument is a "preferred node", which means > > is insufficient space on that node exists to service the GFP_KERNEL > > allocation, it will fall back to another node. > > > > If all hot-plugged memory is added to ZONE_MOVABLE, two things occur: > > > > 1) A portion of the memory block is carved out for to allocate memmap > > data (reducing usable size by 64b*nr_pages) > > > > 2) The memory is allocated on ZONE_NORMAL on another node.. > > Nice write-up, thanks for putting everything together. A follow up > question on this. Do you mean the memmap memory will show up as a new > node with ZONE_NORMAL only besides other hot-plugged memory blocks? So > we will actually see two nodes are hot-plugged? > No, it creates 1 ZONE_MOVABLE memory block of size (BLOCK_SIZE - memmap_size) and as far as i can tell the actual memory map allocations still occur on ZONE_NORMAL (i.e. not CXL). So you just lose the capacity, it's just stranded and unused. > Thanks, > Yang >