On 11/2/2021 3:47 PM, Tudor Cornea wrote:
The poll call can return POLLERR which is ignored, or it can return POLLOUT, even if there are no free frames in the mmap-ed area.We can account for both of these cases by re-checking if the next frame is empty before writing into it. We have attempted to reproduce this issue with pktgen-dpdk, using the following configuration. pktgen -l 1-4 -n 4 --proc-type=primary --no-pci --no-telemetry \ --no-huge -m 512 \ --vdev=net_af_packet0,iface=eth1,blocksz=16384,framesz=8192, \ framecnt=2048,qpairs=1,qdisc_bypass=0 \ -- \ -P \ -T \ -m "3.0" \ -f themes/black-yellow.theme We configure a low tx rate (~ 335 packets / second) and a small packet size, of about 300 Bytes from the pktgen CLI. set 0 size 300 set 0 rate 0.008 set 0 burst 1 start 0 After bringing the interface down, and up again, we seem to arrive in a state in which the tx rate is inconsistent, and does not recover. ifconfig eth1 down; sleep 7; ifconfig eth1 up [1] http://code.dpdk.org/pktgen-dpdk/pktgen-20.11.2/source/INSTALL.md Signed-off-by: Mihai Pogonaru <pogonarumi...@gmail.com> Signed-off-by: Tudor Cornea <tudor.cor...@gmail.com> --- v2: * Added check for POLLERR * Used tx_ring_status_available() for checking TP_STATUS_AVAILABLE --- drivers/net/af_packet/rte_eth_af_packet.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c index 559f5a0..d3d3104 100644 --- a/drivers/net/af_packet/rte_eth_af_packet.c +++ b/drivers/net/af_packet/rte_eth_af_packet.c @@ -237,8 +237,30 @@ eth_af_packet_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) }/* point at the next incoming frame */- if (!tx_ring_status_available(ppd->tp_status) && - poll(&pfd, 1, -1) < 0) + if (!tx_ring_status_available(ppd->tp_status)) { + if (poll(&pfd, 1, -1) < 0) + break; + if (pfd.revents & POLLERR) + break; + } + + /* + * Poll can return POLLERR if the interface is down + *
Above comment fits better to above check, or can remove it completely. Can you send a new version, or I can remove it while merging if you prefer? Except from above comment, Reviewed-by: Ferruh Yigit <ferruh.yi...@intel.com>
+ * It will almost always return POLLOUT, even if there + * are no extra buffers available + * + * This happens, because packet_poll() calls datagram_poll() + * which checks the space left in the socket buffer and, + * in the case of packet_mmap, the default socket buffer length + * doesn't match the requested size for the tx_ring. + * As such, there is almost always space left in socket buffer, + * which doesn't seem to be correlated to the requested size + * for the tx_ring in packet_mmap. + * + * This results in poll() returning POLLOUT. + */ + if (!tx_ring_status_available(ppd->tp_status)) break;/* copy the tx frame data */
