I'm debugging strange delays during transmit in stmmac driver. They
seem to be present in 4.4 kernel (and older kernels, too). Workload is
burst of udp packets being sent, pause, burst of udp packets, ...
Test code is attached, I use these parameters for testing:
./udp-test raw 10.0.0.6 1234 1000 100 30
The delays seem to be related to coalescing:
#define STMMAC_COAL_TX_TIMER 40000
#define STMMAC_MAX_COAL_TX_TICK 100000
#define STMMAC_TX_MAX_FRAMES 256
If I lower the parameters, delays are gone, but I get netdev watchdog
backtrace followed by broken driver.
Any ideas what is going on there?
[I'm currently trying to get newer kernels working on affected