Re: [patch net-next RFC 0/4] net: sched: allow qdiscs to share filter block instances

[Jiri Pirko <jiri@resnulli.us>]

Tue, Jul 11, 2017 at 02:15:27PM CEST, jhs@mojatatu.com wrote:
>Hi Jiri,
>
>Commenting on generalities - will comment on code later:
>
>On 17-07-10 02:51 PM, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@mellanox.com>
>> 
>> Currently the filters added to qdiscs are independent. So for example if you
>> have 2 netdevices and you create ingress qdisc on both and you want to add
>> identical filter rules both, you need to add them twice. This patchset
>> makes this easier and mainly saves resources allowing to share all filters
>> within a qdisc - I call it a "filter block". Also this helps to save
>> resources when we do offload to hw for example to expensive TCAM.
>> 
>> So back to the example. First, we create 2 qdiscs. Both will share
>> block number 22. "22" is just an identification. If we don't pass any
>> block number, a new one will be generated by kernel:
>> 
>> $ tc qdisc add dev ens7 ingress block 22
>>                                  ^^^^^^^^
>> $ tc qdisc add dev ens8 ingress block 22
>> 
>
>Above makes intuitive sense.
>
>
>                                  ^^^^^^^^
>> 
>> Now if we list the qdiscs, we will see the block index in the output:
>> qdisc fq_codel 0: dev ens7 root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn
>>   Sent 9014 bytes 99 pkt (dropped 0, overlimits 0 requeues 0)
>>   backlog 0b 0p requeues 0
>>    maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0
>>    new_flows_len 0 old_flows_len 0
>> qdisc ingress ffff: dev ens7 parent ffff:fff1 block 22
>>                                                ^^^^^^^^
>>   Sent 4592 bytes 58 pkt (dropped 0, overlimits 0 requeues 0)
>>   backlog 0b 0p requeues 0
>> qdisc fq_codel 0: dev ens8 root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms memory_limit 32Mb ecn
>>   Sent 17022 bytes 307 pkt (dropped 0, overlimits 0 requeues 0)
>>   backlog 0b 0p requeues 0
>>    maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0
>>    new_flows_len 0 old_flows_len 0
>> qdisc ingress ffff: dev ens8 parent ffff:fff1 block 22
>>                                                ^^^^^^^^
>>   Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>>   backlog 0b 0p requeues 0
>> 
>
>So does this.
>
>> 
>> Now we can add filter to any of qdiscs sharing the same block:
>> 
>> $ tc filter add dev ens7 parent ffff: protocol ip pref 25 flower dst_ip 192.168.0.0/16 action drop
>> 
>
>So for backward compat - this also makes sense. But:
>it does make sense to create new syntax for adding
>filters and actions:
>
>tc filter add block 22 protocol ip pref 25 flower \
>  dst_ip 192.168.0.0/16 action drop

Was thinking about that. Decided to pass on this now. This should be
addressed by follow-up anyway.


>
>Coordinates of the filter block before were:
>
><ifindex>, <parent>, [handle]
>
>You should be able to abuse struct tcmsg ifindex to represent block #
>as long as you set parent to be something meaningful that is
>identified "block coordinate" via TC_H_XXX (pick something safe not
>in use by ingress or egress; look at: uapi/linux/pkt_sched.h)

Not sure about this. I have take closer look. In general, I don't like
to abuse anything :)


>
>> 
>> We will see the same output if we list filters for ens7 and ens8, including stats:
>> 
>> $ tc -s filter show dev ens7 root
>> filter parent ffff: protocol ip pref 25 flower
>> filter parent ffff: protocol ip pref 25 flower handle 0x1
>>    eth_type ipv4
>>    dst_ip 192.168.1.0/24
>>          action order 1: gact action drop
>>           random type none pass val 0
>>           index 3 ref 1 bind 1 installed 10201 sec used 10150 sec
>>          Action statistics:
>>          Sent 4200 bytes 50 pkt (dropped 50, overlimits 0 requeues 0)
>>          backlog 0b 0p requeues 0
>> 
>> $ tc -s filter show dev ens8 root
>> filter dev ens7 parent ffff: protocol ip pref 25 flower
>> filter dev ens7 parent ffff: protocol ip pref 25 flower handle 0x1
>>    eth_type ipv4
>>    dst_ip 192.168.1.0/24
>>          action order 1: gact action drop
>>           random type none pass val 0
>>           index 3 ref 1 bind 1 installed 10202 sec used 10152 sec
>>          Action statistics:
>>          Sent 4200 bytes 50 pkt (dropped 50, overlimits 0 requeues 0)
>>          backlog 0b 0p requeues 0
>> 
>> 
>> Issues:
>> - tp->q is set by the device used to add the filter. That has to be resolved.
>>    Impacts the dump (as you can see above)
>> 
>
>I think you have more problems if the dump above is reality;->
>You added to ingress and this is showing egress.

Howcome? I only don't see "dev x" on ens7. That is the only difference,


>
>To complete the thought, dump is:
>
> tc -s filter show block 22

Understood. Again, this should be addressed in follow-up.


>
>cheers,
>jamal
>