From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: Re: [PATCH 1/7] node: Link memory nodes to their compute nodes Date: Thu, 15 Nov 2018 09:50:58 -0800 Message-ID: References: <20181114224921.12123-2-keith.busch@intel.com> <20181115135710.GD19286@bombadil.infradead.org> <20181115145920.GG11416@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20181115145920.GG11416@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org To: Keith Busch Cc: Matthew Wilcox , Linux Kernel Mailing List , Linux ACPI , Linux MM , Greg KH , "Rafael J. Wysocki" , Dave Hansen List-Id: linux-acpi@vger.kernel.org On Thu, Nov 15, 2018 at 7:02 AM Keith Busch wrote: > > On Thu, Nov 15, 2018 at 05:57:10AM -0800, Matthew Wilcox wrote: > > On Wed, Nov 14, 2018 at 03:49:14PM -0700, Keith Busch wrote: > > > Memory-only nodes will often have affinity to a compute node, and > > > platforms have ways to express that locality relationship. > > > > > > A node containing CPUs or other DMA devices that can initiate memory > > > access are referred to as "memory iniators". A "memory target" is a > > > node that provides at least one phyiscal address range accessible to a > > > memory initiator. > > > > I think I may be confused here. If there is _no_ link from node X to > > node Y, does that mean that node X's CPUs cannot access the memory on > > node Y? In my mind, all nodes can access all memory in the system, > > just not with uniform bandwidth/latency. > > The link is just about which nodes are "local". It's like how nodes have > a cpulist. Other CPUs not in the node's list can acces that node's memory, > but the ones in the mask are local, and provide useful optimization hints. > > Would a node mask would be prefered to symlinks? I think that would be more flexible, because the set of initiators that may have "best" or "local" access to a target may be more than 1.