On Mon, Nov 19, 2018 at 09:05:07AM +0530, Anshuman Khandual wrote: > On 11/15/2018 04:19 AM, Keith Busch wrote: > > Heterogeneous memory systems provide memory nodes with latency > > and bandwidth performance attributes that are different from other > > nodes. Create an interface for the kernel to register these attributes > > There are other properties like power consumption, reliability which can > be associated with a particular PA range. Also the set of properties has > to be extensible for the future. Sure, I'm just starting with the attributes available from HMAT, If there are additional possible attributes that make sense to add, I don't see why we can't continue appending them if this patch is okay. > > under the node that provides the memory. If the system provides this > > information, applications can query the node attributes when deciding > > which node to request memory. > > Right but each (memory initiator, memory target) should have these above > mentioned properties enumerated to have an 'property as seen' from kind > of semantics. > > > > > When multiple memory initiators exist, accessing the same memory target > > from each may not perform the same as the other. The highest performing > > initiator to a given target is considered to be a local initiator for > > that target. The kernel provides performance attributes only for the > > local initiators. > > As mentioned above the interface must enumerate a future extensible set > of properties for each (memory initiator, memory target) pair available > on the system. That seems less friendly to use if forces the application to figure out which CPU is the best for a given memory node rather than just provide that answer directly. > > The memory's compute node should be symlinked in sysfs as one of the > > node's initiators. > > Right. IIUC the first patch skips the linking process of for two nodes A > and B if (A == B) preventing association to local memory initiator. Right, CPUs and memory sharing a proximity domain are assumed to be local to each other, so not going to set up those links to itself.
