Pete Heist <[email protected]> writes: > On Apr 6, 2017, at 12:50 PM, Toke Høiland-Jørgensen <[email protected]> wrote: > > Pete Heist <[email protected]> writes: > > The fq_codel qdisc does have support for arbitrary tc filters to replace > the default hashing, BTW. If you don't need the cake shaper, that might > be a solution? > > I see, I found mention of it in Chapter 6 of a draft RFC that it looks > like you wrote, actually > (https://tools.ietf.org/html/draft-ietf-aqm-fq-codel-06#section-6). :) > To try it out, am I heading the right direction by looking at tc > filter’s skbedit action, or is that just for MQ devices? > (http://man7.org/linux/man-pages/man8/tc-skbedit.8.html) > > I also saw this mention of “We are not aware of any deployments > utilising the custom classification feature" > https://tools.ietf.org/html/draft-ietf-aqm-fq-codel-02#section-5.1.1, > so not sure how often this has been tried. :) > > Yeah, haven't actually heard of anyone using the feature in production. > It's basically this section from the 'classful qdiscs' section of 'man > tc': > > When a packet enters a classful qdisc it can be classified to one of > the classes within. Three criteria are available, although not all qdiscs > will use all three: > > tc filters > If tc filters are attached to a class, they are consulted first > for relevant instructions. Filters can match on all fields of a packet > header, as well as on the firewall mark applied by ipchains or iptables. > > So you can basically use the full capabilities of tc-filter in place of > the built-in hashing of fq_codel. The tc-u32 man page has some examples, > which is probably a good starting point. > > If you do try this out and feel like writing up a small > example/tutorial, I'm happy to add a link (or the whole thing) somewhere > on bufferbloat.net :) > > Sure, if I get it working I’ll include an example in my paper,
Awesome! > but I’m still a little confused. Is fq_codel actually a classful > qdisc? Yup. The hash buckets are the classes, basically. You can get per-flow stats by doing `tc -s class show dev eth0` (only works when a flow has built a queue). > I get the part about matching with tc-filter and the u32 selector (as > intuitive as that is :), but am not sure of the action the filter > needs to take. However, I do see the example towards the bottom of the > tc-u32 man page where a hash table is created and filters move packets > into the right buckets. Perhaps it will be eventually decipherable > from this… :) The filter classifies a packet into a class. The 'minor number' of this is the queue number (so needs to be less than the number of flows you configured for fq_codel - 1024 by default). -Toke _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
