[dpdk-dev] Calling rte_eth_rx_burst() multiple times
Younghwan Go
yhwan at ndsl.kaist.edu
Thu Oct 15 10:32:58 CEST 2015
Hi,
I'm pretty new to playing with DPDK. I was trying to see if I can always
receive MAX_BURST packets by calling rte_eth_rx_burst() multiple times
on same <port, queue> pair (code shown below). I'm using DPDK-2.1.0 on 2
dual-port Intel 82599ES 10Gbps NICs with Ubuntu 14.04.3 (kernel
3.13.0-63-generic).
Since packet processing is slower (~10 Gbps) than pure RX speed (~40
Gbps), I assumed rte_eth_rx_burst() would always receive some number of
packets, eventually filling up MAX_BURST. But for multi-core case (4
CPUs, 4 ports), rte_eth_rx_burst() starts to always return 0 after some
time, causing all cores to be blocked forever. Analyzing the DPDK code
(drivers/net/ixgbe/ixgbe_rxtx.c), I'm seeing that inside
ixgbe_rx_scan_hw_ring() function, "rxdp->wb.upper.status.error" always
returns 0 (where is this value set by the way?).
I didn't see this problem for single-core case, in which it returned
MAX_BURST packets at every rte_eth_rx_burst() call. Also, if I break out
of while loop when I receive 0, I keep receiving packets in next <port,
queue> pairs. Does anyone know why this block might happen? Or am I not
allowed to call rte_eth_rx_burst() multiple times on same <port, queue>
pair if I get 0? Any help will be great! Thank you!
------------------------------------------------------------------------
int cnt = MAX_BURST; // MAX_BURST = 32
int off = 0;
do {
ret = rte_eth_rx_burst(port_id, queue_id, &m_table[off], cnt);
if (ret == 0) {
// don't break out but continue
} else if (ret > 0) {
off += ret;
cnt -= ret;
}
} while (cnt > 0);
------------------------------------------------------------------------
Best,
Younghwan
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