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
+ *
+ * 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 */
--
2.7.4
