Keith Busch <keith.busch@xxxxxxxxx> writes: > Heterogeneous memory systems provide memory nodes with different latency > and bandwidth performance attributes. Provide a new kernel interface for > subsystems to register the attributes under the memory target node's > initiator access class. If the system provides this information, applications > may query these attributes when deciding which node to request memory. > > The following example shows the new sysfs hierarchy for a node exporting > performance attributes: > > # tree -P "read*|write*" /sys/devices/system/node/nodeY/classZ/ > /sys/devices/system/node/nodeY/classZ/ > |-- read_bandwidth > |-- read_latency > |-- write_bandwidth > `-- write_latency > > The bandwidth is exported as MB/s and latency is reported in nanoseconds. > Memory accesses from an initiator node that is not one of the memory's > class "Z" initiator nodes may encounter different performance than > reported here. When a subsystem makes use of this interface, initiators > of a lower class number, "Z", have better performance relative to higher > class numbers. When provided, class 0 is the highest performing access > class. How does the definition of performance relate to bandwidth and latency here?. The initiator in this class has the least latency and high bandwidth? Can there be a scenario where both are not best for the same node? ie, for a target Node Y, initiator Node A gives the highest bandwidth but initiator Node B gets the least latency. How such a config can be represented? Or is that not possible? -aneesh
