On Thu, May 30, 2019 at 10:42:54PM +0100, Russell King - ARM Linux admin wrote: > On Thu, May 30, 2019 at 12:51:03PM +0100, Morten Rasmussen wrote: > > On Wed, May 29, 2019 at 07:39:17PM -0400, Andrew F. Davis wrote: > > > On 5/29/19 5:13 PM, Atish Patra wrote: > > > >From: Sudeep Holla <sudeep.holla@xxxxxxx> > > > > > > > >The current ARM DT topology description provides the operating system > > > >with a topological view of the system that is based on leaf nodes > > > >representing either cores or threads (in an SMT system) and a > > > >hierarchical set of cluster nodes that creates a hierarchical topology > > > >view of how those cores and threads are grouped. > > > > > > > >However this hierarchical representation of clusters does not allow to > > > >describe what topology level actually represents the physical package or > > > >the socket boundary, which is a key piece of information to be used by > > > >an operating system to optimize resource allocation and scheduling. > > > > > > > > > > Are physical package descriptions really needed? What does "socket" imply > > > that a higher layer "cluster" node grouping does not? It doesn't imply a > > > different NUMA distance and the definition of "socket" is already not well > > > defined, is a dual chiplet processor not just a fancy dual "socket" or are > > > dual "sockets" on a server board "slotket" card, will we need new names for > > > those too.. > > > > Socket (or package) just implies what you suggest, a grouping of CPUs > > based on the physical socket (or package). Some resources might be > > associated with packages and more importantly socket information is > > exposed to user-space. At the moment clusters are being exposed to > > user-space as sockets which is less than ideal for some topologies. > > Please point out a 32-bit ARM system that has multiple "socket"s. > > As far as I'm aware, all 32-bit systems do not have socketed CPUs > (modern ARM CPUs are part of a larger SoC), and the CPUs are always > in one package. > > Even the test systems I've seen do not have socketed CPUs. > As far as we know, there's none. So we simply have to assume all those systems are single socket(IOW all CPUs reside inside a single SoC package) system. -- Regards, Sudeep
