From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F02E3806A6 for ; Wed, 29 Jul 2026 18:28:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785349728; cv=none; b=oNdPXyrm6aVPhOFXZHdEMKZgUpBUFqKRzJWE9HRQCnrA0Y4zwE6fRxLy6x1PbTzmdERLoNl6s9FoJI/0vqmfQxmAH0FbDtW4IBWZJIgJzLC9PMlDBiYooA+8fbB3outaAxKb0vespSnEELTw2HXiALrbAq9LySvSzy6fCQ1QS+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785349728; c=relaxed/simple; bh=sb9VkIxUSZ9lLC6apbeCePi/hTJEHIsJPYDrwvWMI6k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QrX4oCuD3KKymmNooN1XoMoKxk6frUaQaolMouxVmHiq5DWAT2lXKH5iHZgNuJ9uZbrncPiSAvagtsY8WeBqNyeaTABNKxd7ZpbIsDAC2VxKoIe5bRqpHDgvwvy8OYUy8mgLOn/dDGeZIM/p88NHlzQaGrtlOnWw1By4Io59kGc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=OYDUqxSF; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OYDUqxSF" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=oRnzRJMDZ8iuZ3LQn8T44elp+xM+94WMNYL4egIn6js=; b=OYDUqxSFh7l5uF3hrR+GNzddO4 IFnHCZtBQfpOpowmx1ZA4Twp9S8VJyLoFvJSgAq2/CIs5HvGc3fORKqRYBKscvjuE1pKaTN5HUjr+ YcGpcJNHV2dD7h11tSd85LRzO5OMKFOL6SV5XvJMe02JDXrEcQqeaHJ1/1TVlh4s8o3ziye5120jd JgO285Vd8Cp9lB5V5N2CIObEICB7rPPUDQY25ooiTtOXwuFBoET0CHS+wHsf/Cs3Th+24fOH/2MZ3 nAlaMJppv6WXN312cZ2yMSEOnlSnTwj02dbWyQ/Fv3A7v2LdO3aC0idqkbUs+oE0Ll0IWg7H7FZZ3 E7nnsd/Q==; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260729175708.7074-1-iprintercanon@gmail.com> 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?