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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-92e801bbec0sm236826085a.45.2026.07.02.07.43.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jul 2026 07:43:39 -0700 (PDT) Date: Thu, 2 Jul 2026 10:43:34 -0400 From: Gregory Price To: Mike Rapoport Cc: linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, driver-core@lists.linux.dev, kernel-team@meta.com, corbet@lwn.net, skhan@linuxfoundation.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, gregkh@linuxfoundation.org, dakr@kernel.org, akpm@linux-foundation.org, rdunlap@infradead.org, feng.tang@linux.alibaba.com, dapeng1.mi@linux.intel.com, elver@google.com, kuba@kernel.org, ebiggers@kernel.org, lirongqing@baidu.com, paulmck@kernel.org, dave.jiang@intel.com, jic23@kernel.org, xueshuai@linux.alibaba.com, kai.huang@intel.com Subject: Re: [RFC PATCH 1/3] mm/numa: add exclusive node pool and numa=standby boot parameter Message-ID: References: <20260610014517.253609-1-gourry@gourry.net> <20260610014517.253609-2-gourry@gourry.net> Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jul 02, 2026 at 02:09:06PM +0300, Mike Rapoport wrote: > On Tue, Jun 23, 2026 at 12:36:19PM -0400, Gregory Price wrote: > > On Sun, Jun 14, 2026 at 12:08:31PM +0300, Mike Rapoport wrote: > > > On Thu, Jun 11, 2026 at 10:04:01AM -0400, Gregory Price wrote: > > > > On Thu, Jun 11, 2026 at 12:00:17PM +0300, Mike Rapoport wrote: > > > > > > > So really i think you're pointing out that futex_init() here probably > > > > shouldn't be using num_possible_nodes? > > > > > > I'd rather say that num_possible_nodes() with and without CXL (or other > > > differentiated memory) has different semantics. > > > Maybe we need to add a new primitive for possible differentiated nodes and > > > keep num_possible_nodes() to mean "number of possible nodes with normal > > > memory". > > > > > > > We'd have to define "normal" here a little more discretely. > > > > Normal = N_MEMORY at __init? > > Normal = N_MEMORY in the future? > > Normal = not differentiated, no matter at __init or in the future. > I.e. memory that kernel will use with existing allocation primitives. > > > We also use the possible_nodes() mask to allocate per-node pgdat, so > > the futex example is largely just another "hey look at this thing, > > I wonder what other stuff is out there". > > Right, futex is only one example. My point is that with multiplication of > possible and not populated nodes the possible_nodes() mask may not reflect > adequately the limits its callers look for. > > And that maybe it's time to audit possible_nodes() callers. > Totally reasonable, I have been thinking the same thing. ~Gregory