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Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wp91A-0000000Avaq-3Olf; Wed, 29 Jul 2026 18:28:36 +0000 Date: Wed, 29 Jul 2026 19:28:36 +0100 From: Matthew Wilcox To: Artem Lytkin Cc: linux-mm@kvack.org, akpm@linux-foundation.org, urezki@gmail.com, shivamkalra98@zohomail.in, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmalloc: make vm_struct.nr_pages an unsigned long Message-ID: References: <20260729175708.7074-1-iprintercanon@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260729175708.7074-1-iprintercanon@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BCBD640012 X-Stat-Signature: jbr915mtttp3nnz4wggjxgxegq6dqbr6 X-HE-Tag: 1785349720-592913 X-HE-Meta: U2FsdGVkX1/Ql5ardENFZczPhDIrdvRj2P5hmMYo2Xj2/g+BdaSfl+bGfE77YPD2BKQYuHKIGzMMn/JIk+uMHLK9wke2uiWIHV4o9aoAMCE1vf2p3FSjsiNbDLPaiW90fhy/1UBgw1xbaxFR/g/yk60150zzO4IehJyfg/i01uXV3F095h83sYB/Ql7UyjF7Ysj6qOLemxCGb4/TzbvknOrTHvNr4kusG3tPYWhKw+L+S3HSXumfdrMEuSh8PEuFTrWdPYLFByWmMElK5WSq/B56CoyG4WqZXXSG46/NmPPlHP0VcdGOSGEL1fetyCea4jcfj/nuh1LtFgAWG2jFBG65kkTbtCEZt4mde1W4law3I79Z4ELGb3DisrpBFgeo4vmudz+zaXpflnbn5Mgp1d4F8/GD+3bYoapMi7Q5Qkko0FPo2ii5JLkaKAwAuFpPZvFcL9VZbTyoqxkCM9YO2pmL6IwxVe96wyoBbjMdammP4LmoFu2vWUQyGx3eLm3KutdSgJR4vQpQ00UJJk5VDbGuoTgyF2YOlnmWrEbXve0GAGQGoq2eINkj5USXGnAPsE3KrN4+877RXUYN8+j3/7XCJ9lZNmTEjf7/9ZvcMV2IGLwM1XJ46FYwnqd+q9K+uPTLg9ilPv4xxb+6M4P7p79T2zhJW9TWQssc8bTLAOAEKOuhvpIJau01xEcrsnqGWycSHeNWlJbUHb5GiMVLv57pxuXB5+HkPTWaK/+7FqTxdHwLPQ5oIjUJTRAIebfPaJRx8XsGUsLvR4TTvO5LbDJiEWqmr8wZKc/iYvUTz3btRWnoOnG7nbKR5YIgkwwpfNJPW9uozZCRQf06TqhYSmQdKcW9CJGSljRhuGdQSpqCE25okD2/fIbx8WXVhAilINefk51AzVzX2McT6+oEhEqkN5IrkpfDWtMTq1kKR0/p90UBj3aQ9IyNdn1eQ9TD+Pt64OwI715vFpqi6pT OWie46qS 9KRHs4DqcksIP6FpAB5e30ufNrrh0ZavawF25L539wxDFuGuiwNYBG6MEUzXerGzRfMLXqA4zt26G+TahndIZdQ9fODFgn7GTjiEdazFl9Kwd2YYi1xdCHK/IVbQyRtDQc7rKfaW0ZRH2QK5co1iC/c7HWK0Pqy18hUffplM+n5Z+55fVVNrq7YvezWCLq2fDNNV5KFIb0IerK61eVFbkh6N0EZqPfctj3S4ts7haeg7lRABsECQodYgz56gJw1vSN/H5Q2H9FV8DGLgdsz39OtUFlm1go+blnsB9ML8AHnQw1xVRi7YBL/mnMbq9Pel9/J/j2Jjn+Q5V4dc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 29, 2026 at 08:57:08PM +0300, Artem Lytkin wrote: > A vmalloc area can hold more than 2^32 pages, but the page counts I had a "wait, what, really?" moment. And it can! 2^32 pages is 16TiB, and x86-64 says: ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base) So we can have _one_ allocation that is more than 2^32 pages. But I'm not sure where we'll get the memory to populate it from. https://blogs.oracle.com/cloud-infrastructure/announcing-oci-compute-e6-acceleron-instances says I can get 2.3TB of memory in a single machine, which is a factor of 8 away from where we'd need to be to actually hit this. Intel are adveertising a max memory of 1.5TiB on the 6990E+ (128GiB * 12 channels). So if you put 8 Xeons in a box and loaded it up, that could get you to 12TiB. I'm not saying we shouldn't fix this, but it's all theoretical for now, right?