netdev - Re: [RFC PATCH net-next 0/6] implement kthread based napi poll

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Message-ID: <20200925111627.047f5ed2@hermes.lan>
Date:   Fri, 25 Sep 2020 11:16:27 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Wei Wang <weiwan@...gle.com>
Cc:     Magnus Karlsson <magnus.karlsson@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Felix Fietkau <nbd@....name>,
        Björn Töpel <bjorn.topel@...el.com>
Subject: Re: [RFC PATCH net-next 0/6] implement kthread based napi poll

On Fri, 25 Sep 2020 10:15:25 -0700
Wei Wang <weiwan@...gle.com> wrote:

> > > In terms of performance, I ran tcp_rr tests with 1000 flows with
> > > various request/response sizes, with RFS/RPS disabled, and compared
> > > performance between softirq vs kthread. Host has 56 hyper threads and
> > > 100Gbps nic.

It would be good to similar tests on othere hardware. Not everyone has
server class hardware. There are people running web servers on untuned
servers over 10 years old; this may cause a regression there.

Not to mention the slower CPU's in embedded systems. How would this
impact OpenWrt or Android?

Another potential problem is that if you run real time (SCH_FIFO)
threads they have higher priority than kthread. So for that use
case, moving networking to kthread would break them.