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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c5f765ad89sm667321785a.16.2025.04.01.08.17.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Apr 2025 08:17:01 -0700 (PDT) Date: Tue, 1 Apr 2025 11:16:59 -0400 From: Gregory Price To: David Hildenbrand Cc: dan.j.williams@intel.com, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, vishal.l.verma@intel.com, dave.jiang@intel.com, linux-cxl@vger.kernel.org Subject: Re: [PATCH] DAX: warn when kmem regions are truncated for memory block alignment. Message-ID: References: <20250321180731.568460-1-gourry@gourry.net> <3e3115c0-c3a2-4ec2-8aea-ee1b40057dd6@redhat.com> <4d051167-9419-43fe-ab80-701c3f46b19f@redhat.com> Precedence: bulk X-Mailing-List: linux-cxl@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: <4d051167-9419-43fe-ab80-701c3f46b19f@redhat.com> On Tue, Apr 01, 2025 at 04:50:40PM +0200, David Hildenbrand wrote: > > Oh, you mean with the whole memmap_on_memory thing. Even with that, using > 2GB memory blocks would only fit a single 1GB memory block ... and it > requires ZONE_NORMAL. > > For ordinary boot memory, the 1GB behavior should be independent of the > memory block size (a 1GB page can span multiple blocks as long as they are > in the same zone), which is the most important thing. > > So I don't think it's a concern for DAX right now. Whoever needs that, can > disable the memmap_on_memory option. > If we think it's not a major issue then I'll rebase onto latest and push a v9. I think there was one minor nit left. I suppose folks can complain to their vendors about alignment if they don't want 60000 memoryN entries on their huge-memory-systems. Probably we still want this warning? Silent truncation still seems undesirable. ~Gregory