netdev - Re: [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support

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Date:   Tue, 09 Jun 2020 22:31:19 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        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: [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support

Hangbin Liu <liuhangbin@...il.com> writes:

> On Mon, Jun 08, 2020 at 05:32:54PM +0200, Toke Høiland-Jørgensen wrote:
>> Hangbin Liu <liuhangbin@...il.com> writes:
>> 
>> > On Thu, Jun 04, 2020 at 06:02:54PM +0200, Toke Høiland-Jørgensen wrote:
>> >> Hangbin Liu <liuhangbin@...il.com> writes:
>> >> 
>> >> > On Thu, Jun 04, 2020 at 02:37:23PM +0200, Toke HÃƒÂ¸iland-JÃƒÂ¸rgensen wrote:
>> >> >> > Now I use the ethtool_stats.pl to count forwarding speed and here is the result:
>> >> >> >
>> >> >> > With kernel 5.7(ingress i40e, egress i40e)
>> >> >> > XDP:
>> >> >> > bridge: 1.8M PPS
>> >> >> > xdp_redirect_map:
>> >> >> >   generic mode: 1.9M PPS
>> >> >> >   driver mode: 10.4M PPS
>> >> >> 
>> >> >> Ah, now we're getting somewhere! :)
>> >> >> 
>> >> >> > Kernel 5.7 + my patch(ingress i40e, egress i40e)
>> >> >> > bridge: 1.8M
>> >> >> > xdp_redirect_map:
>> >> >> >   generic mode: 1.86M PPS
>> >> >> >   driver mode: 10.17M PPS
>> >> >> 
>> >> >> Right, so this corresponds to a ~2ns overhead (10**9/10400000 -
>> >> >> 10**9/10170000). This is not too far from being in the noise, I suppose;
>> >> >> is the difference consistent?
>> >> >
>> >> > Sorry, I didn't get, what different consistent do you mean?
>> >> 
>> >> I meant, how much do the numbers vary between each test run?
>> >
>> > Oh, when run it at the same period, the number is stable, the range is about
>> > ~0.05M PPS. But after a long time or reboot, the speed may changed a little.
>> > Here is the new test result after I reboot the system:
>> >
>> > Kernel 5.7 + my patch(ingress i40e, egress i40e)
>> > xdp_redirect_map:
>> >   generic mode: 1.9M PPS
>> >   driver mode: 10.2M PPS
>> >
>> > xdp_redirect_map_multi:
>> >   generic mode: 1.58M PPS
>> >   driver mode: 7.16M PPS
>> >
>> > Kernel 5.7 + my patch(ingress i40e, egress i40e + veth(No XDP on peer))
>> > xdp_redirect_map:
>> >   generic mode: 2.2M PPS
>> >   driver mode: 14.2M PPS
>> 
>> This looks wrong - why is performance increasing when adding another
>> target? How are you even adding another target to regular
>> xdp_redirect_map?
>> 
> Oh, sorry for the typo, the numbers make me crazy, it should be only
> ingress i40e, egress veth. Here is the right description:
>
> Kernel 5.7 + my patch(ingress i40e, egress i40e)
> xdp_redirect_map:
>   generic mode: 1.9M PPS
>   driver mode: 10.2M PPS
>
> xdp_redirect_map_multi:
>   generic mode: 1.58M PPS
>   driver mode: 7.16M PPS
>
> Kernel 5.7 + my patch(ingress i40e, egress veth(No XDP on peer))
> xdp_redirect_map:
>   generic mode: 2.2M PPS
>   driver mode: 14.2M PPS

A few messages up-thread you were getting 4.15M PPS in this case - what
changed? It's inconsistencies like these that make me suspicious of the
whole set of results :/

Are you getting these numbers from ethtool_stats.pl or from the XDP
program? What counter are you looking at, exactly?

-Toke