Re: [dpdk-dev] rte_flow update support?

[Tom Barbette <barbette@kth.se>]

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?

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.