[dpdk-dev] rte_flow ageing

[David Bouyeure]

Hi,

I've found out the pretty useful experimental brand new flow ageing API 
implemented in the mlx5 PMD.

I'm trying it (rte_eth_dev_callback_register(RTE_ETH_EVENT_FLOW_AGED), 
RTE_FLOW_ACTION_TYPE_AGE) to recover any flow that I previously offloaded.

The DPDK version is 20.08 and Mellanox(Connect-X6) OFED drivers are 
5.1-2.5.8.0.

I eventually don't see the usefulness of the callback since it's 
actually triggered indirectly by us(the DPDK application) when calling 
rte_flow_get_aged_flows(). If we don't call it, the callback is called 
only once.

And, calling rte_flow_get_aged_flows() from the callback won't trigger 
it next time(MLX5_AGE_TRIGGER is reset after the callback call)

Furthermore, I don't see the point of computing ageing flows in 
mlx5_fow.c::mlx5_flow_aging_check() if the client callback isn't called.

So far, I can handle the flow ageing from the same thread as the one 
which is handling the flow direction(rte_flow), it even avoid threads 
synchronization. But, in the future, I may need to be noticed as soon as 
possible of a single flow ageing, and thus handle this flow logic from 
the ageing callback.


I may misunderstand the whole ageing API... Thanks a lot for any 
clarification.