On 19 Jul 2019, at 16:54, Ilya Maximets wrote:
On 18.07.2019 23:11, William Tu wrote:
The patch introduces experimental AF_XDP support for OVS netdev.
AF_XDP, the Address Family of the eXpress Data Path, is a new Linux
socket
type built upon the eBPF and XDP technology. It is aims to have
comparable
performance to DPDK but cooperate better with existing kernel's
networking
stack. An AF_XDP socket receives and sends packets from an eBPF/XDP
program
attached to the netdev, by-passing a couple of Linux kernel's
subsystems
As a result, AF_XDP socket shows much better performance than
AF_PACKET
For more details about AF_XDP, please see linux kernel's
Documentation/networking/af_xdp.rst. Note that by default, this
feature is
not compiled in.
Signed-off-by: William Tu <u9012...@gmail.com>
Thanks, William, Eelco and Ben!
I fixed couple of things and applied to master!
Good to see this got merged into master while on PTO. However, when I
got back I decided to test it once more…
When testing PVP I got a couple of packets trough, and then it would
stall. I thought it might be my kernel, so updated to yesterdays latest,
no luck…
I did see a bunch of “eno1: send failed due to exhausted memory
pool.” messages in the log. Putting back patch v14, made my problems
go away…
After some debugging, I noticed the problem was with the “continue”
case in the afxdp_complete_tx() function.
Applying the following patch made it work again:
diff --git a/lib/netdev-afxdp.c b/lib/netdev-afxdp.c
index b7cc0d988..9b335ddf0 100644
--- a/lib/netdev-afxdp.c
+++ b/lib/netdev-afxdp.c
@@ -823,16 +823,21 @@ afxdp_complete_tx(struct xsk_socket_info
*xsk_info)
if (tx_to_free == BATCH_SIZE || j == tx_done - 1) {
umem_elem_push_n(&umem->mpool, tx_to_free, elems_push);
xsk_info->outstanding_tx -= tx_to_free;
tx_to_free = 0;
}
}
+ if (tx_to_free) {
+ umem_elem_push_n(&umem->mpool, tx_to_free, elems_push);
+ xsk_info->outstanding_tx -= tx_to_free;
+ }
+
if (tx_done > 0) {
xsk_ring_cons__release(&umem->cq, tx_done);
} else {
COVERAGE_INC(afxdp_cq_empty);
}
}
Which made me wonder why we do mark elements as being used? To my
knowledge (and looking at some of the code and examples), after the
xsk_ring_cons__release() function a xsk_ring_cons__peek() should not
receive any duplicate slots.
I see a rather high number of afxdp_cq_skip, which should to my
knowledge never happen?
$ ovs-appctl coverage/show | grep xdp
afxdp_cq_empty 0.0/sec 339.600/sec 5.6606/sec
total: 20378
afxdp_tx_full 0.0/sec 29.967/sec 0.4994/sec
total: 1798
afxdp_cq_skip 0.0/sec 61884770.167/sec 1174238.3644/sec
total: 4227258112
You mentioned you saw this high number in your v15 change notes, did you
do any research on why?
Cheers,
Eelco
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