On Wed, 2016-09-28 at 20:54 -0700, Tom Herbert wrote: > xps_flows maintains a per device flow table that is indexed by the > skbuff hash. The table is only consulted when there is no queue saved in > a transmit socket for an skbuff. > > Each entry in the flow table contains a queue index and a queue > pointer. The queue pointer is set when a queue is chosen using a > flow table entry. This pointer is set to the head pointer in the > transmit queue (which is maintained by BQL). > > The new function get_xps_flows_index that looks up flows in the > xps_flows table. The entry returned gives the last queue a matching flow > used. The returned queue is compared against the normal XPS queue. If > they are different, then we only switch if the tail pointer in the TX > queue has advanced past the pointer saved in the entry. In this > way OOO should be avoided when XPS wants to use a different queue.
There is something I do not understand with this. If this OOO avoidance is tied to BQL, it means that packets sitting in a qdisc wont be part of the detection. So packets of flow X could possibly be queued on multiple qdiscs.
