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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e8f715b475sm57816386d6.75.2025.03.10.07.13.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Mar 2025 07:14:00 -0700 (PDT) Date: Mon, 10 Mar 2025 10:13:58 -0400 From: Gregory Price To: Rakie Kim Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, joshua.hahnjy@gmail.com, dan.j.williams@intel.com, ying.huang@linux.alibaba.com, kernel_team@skhynix.com, honggyu.kim@sk.com, yunjeong.mun@sk.com Subject: Re: [PATCH 0/4] mm/mempolicy: Add memory hotplug support in weighted interleave Message-ID: References: <20250310090407.631-1-rakie.kim@sk.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: <20250310090407.631-1-rakie.kim@sk.com> On Mon, Mar 10, 2025 at 06:03:59PM +0900, Rakie Kim wrote: > On Fri, 7 Mar 2025 16:55:40 -0500 Gregory Price wrote: > > On Fri, Mar 07, 2025 at 10:56:04AM -0500, Gregory Price wrote: > > > > > > I think the underlying issue you're dealing with is that the system is > > > creating more nodes for you than it should. > > > > > > > Looking into this for other reasons, I think you are right that multiple > > numa nodes can exist that cover the same memory - just different > > regions. > > > > I understand your concerns, and I agree that the most critical issue at the > moment is that the system is generating more nodes than necessary. > We need to conduct a more thorough analysis of this problem, but a detailed > investigation will require a significant amount of time. In this context, > these patches might offer a quick solution to address the issue. > I dug into the expected CEDT / CFMWS behaviors and had some discussions with Dan and Jonathan - assuming your CEDT has multiple CFMWS to cover the same set of devices, this is the expected behavior. https://lore.kernel.org/linux-mm/Z226PG9t-Ih7fJDL@gourry-fedora-PF4VCD3F/T/#m2780e47df7f0962a79182502afc99843bb046205 Basically your BIOS is likely creating one per device and likely one per host bridge (to allow intra-host-bridge interleave). This puts us in an awkward state, and I need some time to consider whether we should expose N_POSSIBLE nodes or N_MEMORY nodes. Probably it makes sense to expose N_MEMORY nodes and allow for hidden state, as the annoying corner condition of a DCD coming and going most likely means a user wouldn't be using weighted interleave anyway. So if you can confirm what you CEDT says compared to the notes above, I think we can move forward with this. ~Gregory