Messages in this thread | | | From | Dave Taht <> | Date | Mon, 14 Nov 2022 05:18:01 -0800 | Subject | Re: [PATCH net-next v3 1/4] net: dsa: add support for DSA rx offloading via metadata dst |
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On Mon, Nov 14, 2022 at 4:21 AM Felix Fietkau <nbd@nbd.name> wrote: > > On 14.11.22 12:55, Vladimir Oltean wrote: > > On Sat, Nov 12, 2022 at 12:13:15PM +0100, Felix Fietkau wrote: > >> On 12.11.22 05:40, Jakub Kicinski wrote: > >> I don't really see a valid use case in running generic XDP, TC and NFT on a > >> DSA master dealing with packets before the tag receive function has been > >> run. And after the tag has been processed, the metadata DST is cleared from > >> the skb. > > > > Oh, there are potentially many use cases, the problem is that maybe > > there aren't as many actual implementations as ideas? At least XDP is, > > I think, expected to be able to deal with DSA tags if run on a DSA > > master (not sure how that applies when RX DSA tag is offloaded, but > > whatever). Marek Behun had a prototype with Marvell tags, not sure how > > far that went in the end: > > https://www.mail-archive.com/netdev@vger.kernel.org/msg381018.html > > In general, forwarding a packet to another switch port belonging to the > > same master via XDP_TX should be relatively efficient. > In that case it likely makes sense to disable DSA tag offloading > whenever driver XDP is being used. > Generic XDP probably doesn't matter much. Last time I tried to use it > and ran into performance issues, I was told that it's only usable for > testing anyway and there was no interest in fixing the cases that I ran > into.
XDP continues to evolve rapidly, as do its use cases. ( ex: ttps://github.com/thebracket/cpumap-pping#readme )
What cases did you run into?
specifically planning to be hacking on the mvpp2 switch driver soon.
> > >> How about this: I send a v4 which uses skb_dst_drop instead of skb_dst_set, > >> so that other drivers can use refcounting if it makes sense for them. For > >> mtk_eth_soc, I prefer to leave out refcounting for performance reasons. > >> Is that acceptable to you guys? > > > > I don't think you can mix refcounting at consumer side with no-refcounting > > at producer side, no? > skb_dst_drop checks if refcounting was used for the skb dst pointer. > > > I suppose that we could leave refcounting out for now, and bug you if > > someone comes with a real need later and complains. Right now it's a bit > > hard for me to imagine all the possibilities. How does that sound? > Sounds good. I think I'll send v4 anyway to deal with the XDP case and > to switch to skb_dst_drop. > > - Felix
-- This song goes out to all the folk that thought Stadia would work: https://www.linkedin.com/posts/dtaht_the-mushroom-song-activity-6981366665607352320-FXtz Dave Täht CEO, TekLibre, LLC
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