On Fri, 26 Jul 2013, Stephen Hemminger wrote:
>> I'm writing an application using DPDK that transmits a large number of
>> packets (it doesn't receive any). When I transmit at 2 Gb/sec, everything
>> will run fine for several seconds (receiver is receiving at correct rate),
>> but then the NIC appears to get 'stuck' and doesn't transmit any more
>> packets. In this state, rte_eth_tx_burst() is returning zero (suggesting
>> that there are no available transmit descriptors), but even if I sleep()
>> for a second and try again, rte_eth_tx_burst() still returns 0. It almost
>> appears as if a packet gets stuck in the transmit ring and keeps
>> everything from flowing. I'm using an Intel 82599EB NIC.
>>
> Make sure there is enough memory for mbufs.
> Also what is your ring size and transmit free threshold?
> It is easy to instrument the driver to see where it is saying "no space left"
> Also be careful with threshold values, many values of pthresh/hthresh/wthresh
> don't work. I would check the Intel reference manual for your hardware.
Thanks for the tips. I don't think I'm running out of mbufs, but I'll
check that again. I am using these values from one of the examples -
which claim to be correct for the 82599EB.
/*
* These default values are optimized for use with the Intel(R) 82599 10
GbE
* Controller and the DPDK ixgbe PMD. Consider using other values for
other
* network controllers and/or network drivers.
*/
#define TX_PTHRESH 36 /**< Default values of TX prefetch threshold reg. */
#define TX_HTHRESH 0 /**< Default values of TX host threshold reg. */
#define TX_WTHRESH 0 /**< Default values of TX write-back threshold reg.
*/
static const struct rte_eth_txconf tx_conf = {
.tx_thresh = {
.pthresh = TX_PTHRESH,
.hthresh = TX_HTHRESH,
.wthresh = TX_WTHRESH,
},
.tx_free_thresh = 0, /* Use PMD default values */
.tx_rs_thresh = 0, /* Use PMD default values */
};
/*
* Configurable number of RX/TX ring descriptors
*/
#define RTE_TEST_TX_DESC_DEFAULT 512
static uint16_t nb_txd = RTE_TEST_TX_DESC_DEFAULT;
