Hi Kevin,
Thanks for review. Some comments inline.
On 16.10.2019 12:15, Kevin Traynor wrote:
Hi Sriram,
Thanks for working on making more fine grained stats for debugging. As
mentioned yesterday, this patch needs rebase so I just reviewed docs and
netdev-dpdk.c which applied. Comments below.
On 21/09/2019 03:40, Sriram Vatala wrote:
OVS may be unable to transmit packets for multiple reasons and
today there is a single counter to track packets dropped due to
any of those reasons. The most common reason is that a VM is
unable to read packets fast enough causing the vhostuser port
transmit queue on the OVS side to become full. This manifests
as a problem with VNFs not receiving all packets. Having a
separate drop counter to track packets dropped because the
transmit queue is full will clearly indicate that the problem
is on the VM side and not in OVS. Similarly maintaining separate
It reads like a bit of a contradiction. On one hand the "The *most
common* reason is that a VM is unable to read packets fast enough".
While having a stat "*will clearly indicate* that the problem is on the
VM side".
counters for all possible drops helps in indicating sensible
cause for packet drops.
This patch adds custom software stats counters to track packets
dropped at port level and these counters are displayed along with
other stats in "ovs-vsctl get interface <iface> statistics"
command. The detailed stats will be available for both dpdk and
vhostuser ports.
I think the commit msg could be a bit clearer, suggest something like
below - feel free to modify (or reject):
OVS may be unable to transmit packets for multiple reasons on the DPDK
datapath and today there is a single counter to track packets dropped
due to any of those reasons.
This patch adds custom software stats for the different reasons packets
may be dropped during tx on the DPDK datapath in OVS.
- MTU drops : drops that occur due to a too large packet size
- Qos drops: drops that occur due to egress QOS
- Tx failures: drops as returned by the DPDK PMD send function
Note that the reason for tx failures is not specificied in OVS. In
practice for vhost ports it is most common that tx failures are because
there are not enough available descriptors, which is usually caused by
misconfiguration of the guest queues and/or because the guest is not
consuming packets fast enough from the queues.
These counters are displayed along with other stats in "ovs-vsctl get
interface <iface> statistics" command and are available for dpdk and
vhostuser/vhostuserclient ports.
Signed-off-by: Sriram Vatala <srira...@altencalsoftlabs.com>
---
v9:...
v8:...
Note that signed-off, --- and version info should be like this ^^^.
otherwise the review version comments will be in the git commit log when
it is applied.
--
Changes since v8:
Addressed comments given by Ilya.
Signed-off-by: Sriram Vatala <srira...@altencalsoftlabs.com>
---
Documentation/topics/dpdk/vhost-user.rst | 13 ++-
lib/netdev-dpdk.c | 81 +++++++++++++++----
utilities/bugtool/automake.mk | 3 +-
utilities/bugtool/ovs-bugtool-get-port-stats | 25 ++++++
.../plugins/network-status/openvswitch.xml | 1 +
5 files changed, 105 insertions(+), 18 deletions(-)
create mode 100755 utilities/bugtool/ovs-bugtool-get-port-stats
diff --git a/Documentation/topics/dpdk/vhost-user.rst
b/Documentation/topics/dpdk/vhost-user.rst
index 724aa62f6..89388a2bf 100644
--- a/Documentation/topics/dpdk/vhost-user.rst
+++ b/Documentation/topics/dpdk/vhost-user.rst
@@ -551,7 +551,18 @@ processing packets at the required rate.
The amount of Tx retries on a vhost-user or vhost-user-client interface can be
shown with::
- $ ovs-vsctl get Interface dpdkvhostclient0 statistics:tx_retries
+ $ ovs-vsctl get Interface dpdkvhostclient0 statistics:netdev_dpdk_tx_retries
I think the "netdev_dpdk_" prefixes should be removed for a few reasons,
- These are custom stats that will only be displayed for the dpdk ports
so they don't need any extra prefix to say they are for dpdk ports
- The 'tx_retries' stat is part of OVS 2.12, I don't like to change its
name to a different one in OVS 2.13 unless there is a very good reason
- The existing stats don't have this type of prefixes (granted most of
them are general stats):
The main reason for the prefix for me is to distinguish those stats
from the stats that comest from the driver/HW. Our new stats has
very generic names that could be named a lot like or even equal to
HW stats. This might be not an issue for vhostuser, but for HW
NICs this may be really confusing for users.
I'm not insisting on 'netdev_dpdk_' prefix, but, IMHO, we need a
way to clearly distinguish those stats. We may use different prefixes
like 'sw_' or just 'ovs_'.
# ovs-vsctl get Interface dpdkvhost0 statistics
{"rx_1024_to_1522_packets"=0, "rx_128_to_255_packets"=0,
"rx_1523_to_max_packets"=0, "rx_1_to_64_packets"=25622176,
"rx_256_to_511_packets"=0, "rx_512_to_1023_packets"=0,
"rx_65_to_127_packets"=0, rx_bytes=1537330560, rx_dropped=0,
rx_errors=0, rx_packets=25622176, tx_bytes=3829825920, tx_dropped=0,
tx_packets=63830432, tx_retries=0}
Also, just to note that if there are changes to existing
interfaces/behaviour it should really mention that in the commit message
so it is highlighted.
+
+When the guest is not able to consume the packets fast enough, the transmit
+queue of the port gets filled up i.e queue runs out of free descriptors.
+This is the most likely reason why dpdk transmit API will fail to send packets
+besides other reasons.
+
+The amount of tx failure drops on a dpdk vhost/physical interface can be
+shown with::
+
+ $ ovs-vsctl get Interface dpdkvhostclient0 \
+ statistics:netdev_dpdk_tx_failure_drops
The commit msg/docs are only focusing on one stat for vhost ports, but
there are other stats and dpdk ports, so they should all get some mention.
I don't feel comfortable for documenting custom stats. This is just because
we can't describe them all. These are things to be changed over time.
And we don't really know what some types of stats means and if they means the
same for different types of HW NICs (they are definitely not) or OVS netdevs
(even within netdev-dpdk).
And that is one more reason to have a prefix for OVS internal statistics on
which we have at least partial control.
I think, that user documentation could mention some special statistics while
describing the troubleshooting for some hard special cases, but this should
not be a glossary of all the possible custom stats. From my point of view,
names of the stats should be as possible self-descriptive and should not
require additional documentation.
BTW, you will not find any description for statistics provided by the linux
or DPDK drivers. You could only look at the driver code or device spec.
Best regards, Ilya Maximets.
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