This patch set introduces transmit flow steering for socketless packets. The idea is that we record the transmit queues in a flow table that is indexed by skbuff hash. The flow table entries have two values: the queue_index and the head cnt of packets from the TX queue. We only allow a queue to change for a flow if the tail cnt in the TX queue advances beyond the recorded head cnt. That is the condition that should indicate that all outstanding packets for the flow have completed transmission so the queue can change.
Tracking the inflight queue is performed as part of DQL. Two fields are added to the dql structure: num_enqueue_ops and num_completed_ops. num_enqueue_ops incremented in dql_queued and num_completed_ops is incremented in dql_completed by the number of operations completed (an new argument to the function). This patch set creates /sys/class/net/eth*/xps_dev_flow_table_cnt which number of entries in the XPS flow table. Note that the functionality here is technically best effort (for instance we don't obtain a lock while processing a flow table entry). Under high load it is possible that OOO packets can still be generated due to XPS if two threads are hammering on the same flow table entry. The assumption of this patches is that OOO packets are not the end of the world and these should prevent OOO in most common use cases with XPS. This is a followup to previous RFC version. Fixes from RFC are: - Move counters to DQL - Fixed typo - Simplified get flow index funtion - Fixed sysfs flow_table_cnt to properly use DEVICE_ATTR_RW - Renamed the mechanism Tested: Manually forced all packets to go through the xps_flows path. Observed that some flows were deferred to change queues because packets were in flight witht the flow bucket. Tom Herbert (4): net: Set SW hash in skb_set_hash_from_sk dql: Add counters for number of queuing and completion operations net: Add xps_dev_flow_table_cnt xps_flows: XPS for packets that don't have a socket include/linux/dynamic_queue_limits.h | 7 ++- include/linux/netdevice.h | 26 ++++++++- include/net/sock.h | 6 +- lib/dynamic_queue_limits.c | 3 +- net/Kconfig | 6 ++ net/core/dev.c | 85 ++++++++++++++++++++++++----- net/core/net-sysfs.c | 103 +++++++++++++++++++++++++++++++++++ 7 files changed, 214 insertions(+), 22 deletions(-) -- 2.8.0.rc2
