Re: [dpdk-dev] rte_flow update support?

[Shahaf Shuler <shahafs@mellanox.com>]

Friday, February 15, 2019 12:46 PM, Tom Barbette:
> Subject: Re: rte_flow update support?
> 
> Hi Shahaf,
> 
> This is great news! I'll definitely stay tuned.
> 
> Is there any way to support replacement with the current system with some
> patching? Eg the driver refuses to overwrite rules with kernel message such
> as "FTE flow tag 196608 already exists with different flow tag 327680". Would
> it be possible to ignore the message and overwrite?

This will require some kernel patches. Not sure you want to go this way. 

> 
> Tom
> 
> On 2019-02-14 14:15, Shahaf Shuler wrote:
> > Hi Tom,
> >
> > Thursday, February 14, 2019 1:31 PM, Tom Barbette:
> >> Subject: rte_flow update support?
> >>
> >> Hi all,
> >>
> >> Are there plans to add support for modifying rules using the rte_flow API
> ?
> >>
> >> The first problem with destroy+create is atomicity. During the
> >> process some packets will get lost.
> >>
> >> Then the second problem is performance. We measured Mellanox CX5
> >> (mlx5
> >> driver) to be able to "update" at best 2K rules/sec, but that drops
> >> to
> >> 200 rules/sec when updating TC rules ("transfer" rules, to switch
> >> packets between VFs). Real support for update should boost those
> numbers.
> >
> > Yes you are right, the current update rate of verbs and TC is not so good.
> >
> >>
> >> I saw the ibverbs API backing the mlx5 supports updating the action of a
> rule.
> >> This would already solve a lot of use cases. Eg, changing destination
> >> queue(s) of some rules. Given that mlx5 does not support changing
> >> global RSS queues without restarting the device, this would also
> >> solve re-balancing issue by using rte_flow.
> >
> > Updating the action list will solve only part of issue, what you really want
> (for OVS case) is to update the flow pattern as well (since TCP connection got
> terminated and new one was created).
> >
> >>
> >> Then, beyond updating only the action of a rule, some researchers
> >> have shown[1] that updating rules patterns data instead of creating
> >> and deleting rules with similar patterns improve drastically the
> >> performance. Eg that could be very interesting to accelerate the
> >> offloading of OVS's flow cache (5- tuples), or similar setups.
> >
> > Stay tuned, we are working on it.
> > There is a new engine for flow rules which will be very fast. Expected
> performance will be ~300K updates per second and will include both transfer
> and regular flow rules.
> > It is in plans for 19.XX releases.
> >
> > Would recommend you to have a try on it once ready.
> >
> >
> >>
> >> Thanks,
> >> Tom
> >>
> >>
> >> [1] Turboflow: information rich flow record generation on commodity
> >> switches,  J Sonchack et al.