> On 04.06.2018 11:07, Eelco Chaudron wrote:
> > When ping-pong'in a live VM migration between two machines running
> > OVS-DPDK every now and then the ping misses would increase
> > dramatically. For example:
> >
> > ===========Stream Rate: 3Mpps=========== No Stream_Rate Downtime
> > Totaltime Ping_Loss Moongen_Loss
> > 0 3Mpps 128 13974 115 7168374
> > 1 3Mpps 145 13620 17 1169770
> > 2 3Mpps 140 14499 116 7141175
> > 3 3Mpps 142 13358 16 1150606
> > 4 3Mpps 136 14004 16 1124020
> > 5 3Mpps 139 15494 214 13170452
> > 6 3Mpps 136 15610 217 13282413
> > 7 3Mpps 146 13194 17 1167512
> > 8 3Mpps 148 12871 16 1162655
> > 9 3Mpps 137 15615 214 13170656
> >
> > I identified this issue being introduced in OVS commit,
> > f3e7ec254738 ("Update relevant artifacts to add support for DPDK
> > 17.05.1.") and more specific due to DPDK commit,
> > af1475918124 ("vhost: introduce API to start a specific driver").
> >
> > The combined changes no longer have OVS start the vhost socket polling
> > thread at startup, but DPDK will do it on its own when the first vhost
> > client is started.
> >
> > Figuring out the reason why this happens kept me puzzled for quite some
> time...
> > What happens is that the callbacks called from the vhost thread are
> > calling ovsrcu_synchronize() as part of destroy_device(). This will
> > end-up calling seq_wait__().
> >
> > By default, all created threads outside of OVS will get thread id 0,
> > which is equal to the main ovs thread. So for example in the
> > seq_wait__() function above if the main thread is waiting already we
> > won't add ourselves as a waiter.
> >
> > The fix below assigns OVSTHREAD_ID_UNSET to none OVS created threads,
> > which will get updated to a valid ID on the first call to
> > ovsthread_id_self().
> >
> > Signed-off-by: Eelco Chaudron <[email protected]>
>
>
> Fixes: f3e7ec254738 ("Update relevant artifacts to add support for DPDK
> 17.05.1.")
> Acked-by: Ilya Maximets <[email protected]>
Thanks for this, I've applied to DPDK_MERGE and will backport to 2.9 and 2.8.
Ian
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