[dpdk-dev] vmxnet3 pmd stats counters reset after rte_eth_dev_start() is called

[Tom Crugnale]

Hi All,

I am seeing an issue where the stats counters for vmxnet3 interfaces are reset to 0 after rte_eth_dev_start() is called, making it difficult to track statistics over a period of time where interfaces could be disabled and re-enabled.

There is a memset in the code that clears the txq/rxq stats counters to 0 each time an interface is started from the stopped state.  However, even with this code removed, I still see the issue happening.  I believe there is something on the host side that is resetting these counters, since they come from shared memory.

Does anyone know what causes the reset, and if there is a way to prevent it?  I could work around the issue by caching a snapshot of the last statistics before calling rte_eth_dev_start() and then just using that as a baseline for accumulation going forward, but I don't think this behaviour exists for all other NIC types, so I would have to specialize on the vmxnet3 case.

Thanks,
Tom