Hi! > 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: > > drivers/net/ethernet/stmicro/stmmac/common.h > #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?
4.9-rc6 still has the delays. With the
#define STMMAC_COAL_TX_TIMER 1000
#define STMMAC_TX_MAX_FRAMES 2
settings, delays go away, and driver still works. (It fails fairly
fast in 4.4). Good news. But the question still is: what is going on
there?
Best regards,
Pavel
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