On 4/16/19 4:39 PM, Andrey V. Elsukov wrote:
On 05.12.2018 17:25, Slava Shwartsman wrote:
Author: slavash
Date: Wed Dec 5 14:25:03 2018
New Revision: 341586
URL: https://svnweb.freebsd.org/changeset/base/341586
Log:
mlx5en: Implement backpressure indication.
The backpressure indication is implemented using an unlimited rate type of
mbuf send tag. When the upper layers typically the socket layer has obtained
such
a tag, it can then query the destination driver queue for the current
amount of space available in the send queue.
A single mbuf send tag may be referenced multiple times and a refcount has been added
to the mlx5e_priv structure to track its usage. Because the send tag resides
in the mlx5e_channel structure, there is no need to wait for refcounts to
reach
zero until the mlx4en(4) driver is detached. The channels structure is
persistant
during the lifetime of the mlx5en(4) driver it belongs to and can so be
accessed
without any need of synchronization.
The mlx5e_snd_tag structure was extended to contain a type field, because there are now
two different tag types which end up in the driver which need to be
distinguished.
Submitted by: hselasky@
Approved by: hselasky (mentor)
MFC after: 1 week
Sponsored by: Mellanox Technologies
@@ -587,27 +609,33 @@ mlx5e_xmit(struct ifnet *ifp, struct mbuf *mb)
struct mlx5e_sq *sq;
int ret;
- sq = mlx5e_select_queue(ifp, mb);
- if (unlikely(sq == NULL)) {
-#ifdef RATELIMIT
- /* Check for route change */
- if (mb->m_pkthdr.snd_tag != NULL &&
- mb->m_pkthdr.snd_tag->ifp != ifp) {
+ if (mb->m_pkthdr.snd_tag != NULL) {
+ sq = mlx5e_select_queue_by_send_tag(ifp, mb);
+ if (unlikely(sq == NULL)) {
+ /* Check for route change */
+ if (mb->m_pkthdr.snd_tag->ifp != ifp) {
+ /* Free mbuf */
+ m_freem(mb);
+
+ /*
+ * Tell upper layers about route
+ * change and to re-transmit this
+ * packet:
+ */
+ return (EAGAIN);
+ }
Hi,
I just discovered something strange and found that this commit is the
cause.
The test system has mlx5en 100G interface. It has two vlans: vlan500 and
vlan100.
Via vlan500 it receives some packets flows. Then it routes these packets
into vlan100.
But packets are dropped in mlx5e_xmit() with EAGAIN error code.
# dtrace -n 'fbt::ip6_output:return {printf("%d", arg1);}'
dtrace: description 'fbt::ip6_output:return ' matched 1 probe
CPU ID FUNCTION:NAME
23 54338 ip6_output:return 35
16 54338 ip6_output:return 35
21 54338 ip6_output:return 35
22 54338 ip6_output:return 35
24 54338 ip6_output:return 35
23 54338 ip6_output:return 35
14 54338 ip6_output:return 35
^C
# dtrace -n 'fbt::mlx5e_xmit:return {printf("%d", arg1);}'
dtrace: description 'fbt::mlx5e_xmit:return ' matched 1 probe
CPU ID FUNCTION:NAME
16 69030 mlx5e_xmit:return 35
23 69030 mlx5e_xmit:return 35
26 69030 mlx5e_xmit:return 35
25 69030 mlx5e_xmit:return 35
24 69030 mlx5e_xmit:return 35
21 69030 mlx5e_xmit:return 35
26 69030 mlx5e_xmit:return 35
^C
The kernel config is GENERIC.
13.0-CURRENT #9 r345758+82f3d57(svn_head)-dirty
Hi,
This might be a case where rcvif in the mbuf's pktheader is not cleared
before the packet is fed back on the wire.
John Baldwin is working on the send tags implementation, to eliminate
the EAGAIN handling in the network drivers.
--HPS
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