From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:56884 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2502755AbfIWUfE (ORCPT ); Mon, 23 Sep 2019 16:35:04 -0400 Date: Mon, 23 Sep 2019 22:34:10 +0200 From: Peter Zijlstra Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Message-ID: <20190923203410.GI2369@hirez.programming.kicks-ass.net> References: <1568724534-146242-1-git-send-email-linyunsheng@huawei.com> <20190923151519.GE2369@hirez.programming.kicks-ass.net> <20190923152856.GB17206@dhcp22.suse.cz> <20190923154852.GG2369@hirez.programming.kicks-ass.net> <20190923165235.GD17206@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190923165235.GD17206@dhcp22.suse.cz> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Michal Hocko Cc: Yunsheng Lin , catalin.marinas@arm.com, will@kernel.org, mingo@redhat.com, bp@alien8.de, rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, jiaxun.yang@flygoat.com, chenhc@lemote.com, akpm@linux-foundation.org, rppt@linux.ibm.com, anshuman.khandual@arm.com, tglx@linutronix.de, cai@lca.pw, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, len.brown@intel.com, axboe@kernel.dk, dledford@redhat.com, jeffrey.t.kirsher@intel.com, linux-alpha@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, tbogendoerfer@suse.de, linux-mips@vger.kernel.org, rafael@kernel.org, gregkh@linuxfoundation.org On Mon, Sep 23, 2019 at 06:52:35PM +0200, Michal Hocko wrote: > On Mon 23-09-19 17:48:52, Peter Zijlstra wrote: > To the NUMA_NO_NODE itself. Your earlier email noted: > : > + > : > if ((unsigned)node >= nr_node_ids) { > : > printk(KERN_WARNING > : > "cpumask_of_node(%d): (unsigned)node >= nr_node_ids(%u)\n", > : > : I still think this makes absolutely no sense what so ever. > > Did you mean the NUMA_NO_NODE handling or the specific node >= nr_node_ids > check? The NUMA_NO_NODE thing. It's is physical impossibility. And if the device description doesn't give us a node, then the description is incomplete and wrong and we should bloody well complain about it. > Because as to NUMA_NO_NODE I believe this makes sense because this is > the only way that a device is not bound to any numa node. Which is a physical impossibility. > I even the > ACPI standard is considering this optional. Yunsheng Lin has referred to > the specific part of the standard in one of the earlier discussions. > Trying to guess the node affinity is worse than providing all CPUs IMHO. I'm saying the ACPI standard is wrong. Explain to me how it is physically possible to have a device without NUMA affinity in a NUMA system? 1) The fundamental interconnect is not uniform. 2) The device needs to actually be somewhere. >From these it seems to follow that access to the device is subject to NUMA.