netdev - Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <e1573338-17c0-48f4-b4cd-28eeb7ce699a@gmail.com>
Date:   Wed, 9 Dec 2020 08:41:05 -0700
From:   David Ahern <dsahern@...il.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        alardam@...il.com, magnus.karlsson@...el.com,
        bjorn.topel@...el.com, andrii.nakryiko@...il.com, kuba@...nel.org,
        ast@...nel.org, netdev@...r.kernel.org, davem@...emloft.net,
        hawk@...nel.org, jonathan.lemon@...il.com, bpf@...r.kernel.org,
        jeffrey.t.kirsher@...el.com, maciejromanfijalkowski@...il.com,
        intel-wired-lan@...ts.osuosl.org,
        Marek Majtyka <marekx.majtyka@...el.com>
Subject: Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

On 12/9/20 4:52 AM, Jesper Dangaard Brouer wrote:
>>> still load and either share queues across multiple cores or restirct
>>> down to a subset of CPUs.  
>>
>> And that's the missing piece of logic, I suppose.
>>
>>> Do you need 192 cores for a 10gbps nic, probably not.  
>>
>> Let's hear from Jesper :p
> 
> LOL - of-cause you don't need 192 cores.  With XDP I will claim that
> you only need 2 cores (with high GHz) to forward 10gbps wirespeed small
> packets.

You don't need 192 for 10G on Rx. However, if you are using XDP_REDIRECT
from VM tap devices the next device (presumably the host NIC) does need
to be able to handle the redirect.

My personal experience with this one is mlx5/ConnectX4-LX with a limit
of 63 queues and a server with 96 logical cpus. If the vhost thread for
the tap device runs on a cpu that does not have an XDP TX Queue, the
packet is dropped. This is a really bizarre case to debug as some
packets go out fine while others are dropped.