[ovs-dev] [PATCH v4] Upcall/Slowpath rate-limiter for OVS

Jan Scheurich jan.scheurich at ericsson.com
Fri Jun 8 09:00:39 UTC 2018


>     Have you considered making this token bucket per-port instead of
>     per-pmd?  As I read it, a greedy port can exhaust all the tokens from a
>     particular PMD, possibly leading to an unfair performance for that PMD
>     thread.  Am I just being overly paranoid?
> [manu] Yes, this is possible. But it can happen for both fast and slowpath today, as PMDs sequentially iterate through ports. In order
> to keep it simple, its done per-PMD. It can be extended to per-port if needed.

The purpose of the upcall rate limiter for the netdev datapath is to protect a PMD from becoming clogged down by having to process an excessive number of upcalls. It is not to police the number of upcalls per port to some rate, especially not across multiple PMDs (in the case of RSS).

I think what you are after, Aaron, is some kind of fairness scheme that provides each rx queue with a minimum rate of upcalls even if the global PMD rate limit is reached? I don't believe simply partitioning the global PMD rate limit into a number of smaller rx queue buckets would be a good solution. But I don't have a better alternative either.

I agree with Manu that it should not stop us implementing the PMD-level protection. We can add a fairness scheme later, if needed.

BR, Jan


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