From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DA39B336895 for ; Tue, 3 Mar 2026 21:55:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772574959; cv=none; b=jvUkIWWYbW4UCOIvUlVhG9S2nFaHc5JxMmJeLqHw93e2K3HEp5MfOr3jOIBKoXHs2LtEzgGswVeUVK+G8ry4e/fzU84Dpw+U/C7DrOAujcK5ZTdq8sr9TQPUKzD5IjYq2vCmMMOoNkTwpJ+gU01tNVZ9kNLbFUttyUTi1GsSqww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772574959; c=relaxed/simple; bh=ukGkgzNoxuFBJf39z4xT7tjmFboDYVMiXMfCc6oEqN8=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=RM3i69QNwG2ZWEy+nCa+1UDy+QDTECVRZuU0j3x38FW5VzUHMmSlmDHSyvwNekmgnK9Tpb4BdkrPRanRg7rTJSNYeEiIcsf5jZAuKMfQy6pVe19qn+CgJiNI1J414OlEChalDlsNO9JfdZI1DMSBtfnOkLVXiJsP3hZuILT/+cg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jiu/1D2/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jiu/1D2/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FE7EC116C6; Tue, 3 Mar 2026 21:55:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772574959; bh=ukGkgzNoxuFBJf39z4xT7tjmFboDYVMiXMfCc6oEqN8=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=jiu/1D2/8apAhWOun+Nh0jedBnUue0QDnWOy3H2XsLHV2BFNwk/oV3exTcfggX0AP AY0iNI/d77JhblVZQBL4ej5bC+4CHffqKo7oLYRZtAmOHjFie5qallHmsdLqt/w9cC jXMUOu4jg3Bz9pFCSYSoe2xWYsiPYbOF4DlKkfcL8RUvf8Gk3rPFXZ5v1dgDGux5it PmbERezsEVt+YuoyN6jg5TbhPKjymi6/pNsbEm2phVTgJcVKKM1mScWX85WkYL0E1S rxEfi9pNDppu53eL1lQN/3ugXEIQsRe+T3PpWR2ZdmecigZdg67cDa67lXEfM6oNEa 53bo1i/Hk8Xqg== Date: Tue, 3 Mar 2026 15:55:58 -0600 From: Bjorn Helgaas To: Paul Menzel Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, Yunsheng Lin Subject: Re: Linux warns `Unknown NUMA node; performance will be reduced` Message-ID: <20260303215558.GA4076158@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@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: [+cc Yunsheng, author of ad5086108b9f, +bcc commenters on https://bugzilla.kernel.org/show_bug.cgi?id=218951, see the email thread at https://lore.kernel.org/all/a154f694-c48b-4b3b-809f-4b74ec86a924@molgen.mpg.de] On Sun, Jun 09, 2024 at 10:31:05AM +0200, Paul Menzel wrote: > Dear Linux folks, > > On the servers below Linux warns: > > Unknown NUMA node; performance will be reduced > > 1. [ 0.000000] DMI: Dell Inc. PowerEdge R730/0H21J3, BIOS 2.13.0 > 05/14/2021 > 2. [ 0.000000] DMI: Dell Inc. PowerEdge R730/0H21J3, BIOS 2.2.5 > 09/06/2016 > 3. [ 0.000000] DMI: Dell Inc. PowerEdge R730xd/0WCJNT, BIOS 2.3.4 > 11/08/2016 > 4. [ 0.000000] DMI: Dell Inc. PowerEdge R910/0KYD3D, BIOS 2.10.0 > 08/29/2013 > 5. [ 0.000000] DMI: Dell Inc. PowerEdge R930/0T55KM, BIOS 2.8.1 > 01/02/2020 > 6. [ 0.000000] DMI: Dell Inc. PowerEdge T630/0NT78X, BIOS 2.5.4 > 08/17/2017 > 7. [ 0.000000] DMI: Dell Inc. PowerEdge T630/0W9WXC, BIOS 1.5.4 > 10/04/2015 > 8. [ 0.000000] DMI: Dell Inc. PowerEdge T630/0W9WXC, BIOS 2.11.0 > 12/23/2019 > 9. [ 0.000000] DMI: Dell Inc. PowerEdge T630/0W9WXC, BIOS 2.1.5 > 04/13/2016 > 10. [ 0.000000] DMI: Supermicro Super Server/X13SAE, BIOS 2.0 10/17/2022 Similar reports in the bugzilla for: Host: VMware VM Ubuntu 24.04.1 CPU: Intel(R) Xeon(R) Silver 4310 CPU @ 2.10GHz Kernel: 6.11.0-rc6 and Lenovo P700 workstation 6.19.5 kernel ad5086108b9f ("PCI: Warn if no host bridge NUMA node info") added this "Unknown NUMA node; performance will be reduced" warning. The problem is that firmware didn't tell us anything about which CPUs are closest to this PCI host bridge, so we can't try to optimize by running the driver on a CPU that's close to the device. The kernel can't figure out this locality information itself, so there's nothing we can really do in the kernel, and there's nothing users can do either other than check for BIOS updates. What if we just downgraded the message to "info"? And/or we could reword this to be less alarming. I guess we could even drop the message altogether and assume that vendors will provide the locality information if there's any meaningful performance benefit. It could be that it really doesn't matter where drivers run on these machines, so there's no benefit to providing the locality information. Bjorn