From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 21E442C21D9; Thu, 11 Jun 2026 09:00:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781168433; cv=none; b=MtpNFaOkakRBgILT6HvW55h0ujxxUDEA2J863N7w2Os6VArStQnN2jm+vwCllbxY12OivNqqYT6XswQYttnTzf9wEEwWfVSrvJfLrfrfK3x0DIkBbWM03RHHVM5i3+CYmcJaPfWikB8j7WQqPzvByhr0Eukb4yWsxBfraPAXzxc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781168433; c=relaxed/simple; bh=1M5gUjbpW3qDXO5PZ4+Xq+o9JfPpWnNpLMac6opNScg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HcJtuHw+w655DmWuSJIQAR/tjYBWgLsFQqyft52tKyNvdtOrzgFowjpr3uJ3NjLHMmTmT/mhSvSHQwwiEdsbnab9LJ3qoTyCtTDVI7WfN54LunliUk8/2E4criybcUuwGYu/XcfpvN6x3gmiGMjQ98o4WgVwwJSMKfr4r0qlYqE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Kf9ub8+B; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Kf9ub8+B" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 186571F00893; Thu, 11 Jun 2026 09:00:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781168431; bh=dBiQEyPYgAL0tseH1DOFeKLkbItEWq0+K9vLt73dVTg=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Kf9ub8+BMhfxHSSrYb31ZlyIkUI00iNanropMQakz2F7cdTEYJwi4BZyIu9g2qLzT NAzAyfORVXc/VXPhIsLPZXcp5qYByR74xf7Y/hXstMtTZ9jSnUasCvvbLXj/odVkjk zC+1Fz5dQN88PaAMa8fHTvZf6DzVXfKzdg3/OWkWEYONwhzBNeTTHD8DtWsV1pVz5i f2tC8HgeZRr+znQr5qhxeT4IdkKGvmCJJJoOQDZ2WQrpygnIc1i3Ut7P5XcPLp3UWn SMs+XyHVH9UBKPfyJcs05y1kBY44Dm2+Mj5fwnqDVrCwIxbk4o4eG5Cg/UkxaQZ1Mj c2BmaPxzet9qA== Date: Thu, 11 Jun 2026 12:00:17 +0300 From: Mike Rapoport To: Gregory Price 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: linux-doc@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: <20260610014517.253609-2-gourry@gourry.net> Hi, On Tue, Jun 09, 2026 at 09:45:15PM -0400, Gregory Price wrote: > It can be at times preferential to logically split up hotplug memory > capacity into more nodes than are described by BIOS at boot time. > > However, if nodes are not described at __init time, they are not > possible to add later on. ... > 1) Can we do dynamic addition of nodes? > > Not Trivially > > Some services utilize num_possible_nodes() as a static value to > calculate the amount of resources to use at runtime (bpf, md/raid5). > > Example: futex_init uses num_possible_nodes() as part of its > hashsize calculation during __init. AFAIU, we don't add the additional nodes for generic hotplug memory but rather for exclusive use of by drivers/applications that are aware of these nodes. Wouldn't adding them to possible nodes actually skew the calculation of the resources by the services utilizing num_possible_nodes()? With the futex_init() example, won't be hashsize scaled down two much because we've added these special nodes to the possible mask? -- Sincerely yours, Mike.