On Fri, Jun 28, 2019 at 04:29:36PM +0300, Ilya Maximets wrote:
> On 28.06.2019 16:17, Flavio Leitner wrote:
> > On Fri, Jun 28, 2019 at 03:21:07PM +0300, Ilya Maximets wrote:
> >> On 27.06.2019 14:12, Kevin Traynor wrote:
> >>> vhost tx retries may occur, and it can be a sign that
> >>> the guest is not optimally configured.
> >>>
> >>> Add some stats so a user will know if vhost tx retries are
> >>> occurring and hence give a hint that guest config should be
> >>> examined.
> >>>
> >>> Signed-off-by: Kevin Traynor <[email protected]>
> >>> Acked-by: Flavio Leitner <[email protected]>
> >>> Acked-by: Eelco Chaudron <[email protected]>
> >>> ---
> >>>  Documentation/topics/dpdk/vhost-user.rst | 5 +++++
> >>>  include/openvswitch/netdev.h             | 1 +
> >>>  lib/netdev-dpdk.c                        | 7 +++++--
> >>>  vswitchd/bridge.c                        | 3 ++-
> >>>  4 files changed, 13 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/Documentation/topics/dpdk/vhost-user.rst 
> >>> b/Documentation/topics/dpdk/vhost-user.rst
> >>> index 1dd02b8b6..3caa88231 100644
> >>> --- a/Documentation/topics/dpdk/vhost-user.rst
> >>> +++ b/Documentation/topics/dpdk/vhost-user.rst
> >>> @@ -112,4 +112,9 @@ The guest should also have sufficient cores dedicated 
> >>> for consuming and
> >>>  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
> >>> +
> >>>  .. _dpdk-vhost-user:
> >>>  
> >>> diff --git a/include/openvswitch/netdev.h b/include/openvswitch/netdev.h
> >>> index 0c10f7b48..4d18b9f66 100644
> >>> --- a/include/openvswitch/netdev.h
> >>> +++ b/include/openvswitch/netdev.h
> >>> @@ -46,4 +46,5 @@ struct netdev_stats {
> >>>      uint64_t multicast;         /* Multicast packets received. */
> >>>      uint64_t collisions;
> >>> +    uint64_t tx_retries;        /* Retries when unable to transmit.*/
> >>
> >>
> >> This seems very vhost specific counter.
> >> Maybe it's better to report it in custom_stats?
> > 
> > I thought we could implement retry for nics and rings if we want to
> > not drop any packets. Not sure if it will ever be implemented
> > though.
> 
> For HW NICs, I think, it's unlikely that we'll push packets faster than
> HW will send them. For ring ports it makes more sense, but do you know
> if anyone uses them? Since ivshmem deprecation this functionality looks
> not very interesting. I don't know if anyone uses ring ports at all.

Things might change when we mix with HWOL, but it's hard to tell
today.
 
> Anyway, with custom stats where will be no difference for the user.
> The only difference is in OVS code. At least, there is no re-try
> functionality for system interfaces in both datapaths.

Just wanted to point out that possibility, but that's not the case
today so I have no strong opinion either way.

fbl
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