netdev - Re: [PATCHv6 bpf-next 1/3] xdp: add a new helper for dev map multicast support

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Message-ID: <53bd6672-f70d-086c-7155-d0136b6e8364@gmail.com>
Date:   Sat, 11 Jul 2020 10:09:29 -0600
From:   David Ahern <dsahern@...il.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Subject: Re: [PATCHv6 bpf-next 1/3] xdp: add a new helper for dev map
 multicast support

On 7/10/20 6:26 PM, Hangbin Liu wrote:
>>
>> The point of DEVMAP_HASH is to allow map management where key == device
>> index (vs DEVMAP which for any non-trivial use case is going to require
>> key != device index). You could require the exclude map to be
>> DEVMAP_HASH and the key to be the index allowing you to do a direct
>> lookup. Having to roam the entire map looking for a match does not scale
>> and is going to have poor performance with increasing number of entries.
>> XDP is targeted at performance with expert level of control, so
>> constraints like this have to be part of the deal.
> 
> Yes, if we have this constraints the performance should have some improvement.
> 
> Do you think we should do it right now or in later performance update patch.
> 

It needs to be in the same release as the initial patches. Easiest to
include with the initial set, but a followup is fine if it happens
before this dev cycle is over.