Speed on Raspberry Pi 4

Speed on Raspberry Pi 4

[Christopher Bachner]

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Hello,

I got a Raspberry Pi 4 with 4GB Ram.

I ran some benchmarks. With pure iperf3 I get 950 Mbit/s.

With wireguard in the same network I can only get max 750 Mbit/s (which in
itself is already great).

In htop I can see that one of the 4 cores is running at 99%. So I assume
that is the bottleneck.

[image: image.png]

Is there a way to improve this? I assume it does not matter which side is
the server and which is the client?

Thanks,

Christopher

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Re: Speed on Raspberry Pi 4

[Roman Mamedov]

On Sat, 29 Jun 2019 12:38:01 +0200
Christopher Bachner <hello@chrisbox.org> wrote:

> In htop I can see that one of the 4 cores is running at 99%. So I assume
> that is the bottleneck.
> 
> Is there a way to improve this? I assume it does not matter which side is
> the server and which is the client?

You can see that the load from WireGuard encryption is about 42-43% per each
core. But the thing is, one of them (the 1st) also gets to process interrupt
load from the NIC, and that consumes the rest of it, causing the bottleneck. In
theory, if you could limit WG to run encryption on all cores EXCEPT the first
one, then maaaaybe...

Another way would be to use a NIC which is capable of splitting interrupt load
across multiple CPU cores. But I believe the RPi one can't do that, and no USB
NICs can.

-- 
With respect,
Roman
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Re: Speed on Raspberry Pi 4

[Janne Johansson]

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Den ons 17 juli 2019 kl 22:53 skrev Roman Mamedov <rm@romanrm.net>:

> On Sat, 29 Jun 2019 12:38:01 +0200
> Christopher Bachner <hello@chrisbox.org> wrote:
> > In htop I can see that one of the 4 cores is running at 99%. So I assume
> > that is the bottleneck.
> > Is there a way to improve this? I assume it does not matter which side is
> > the server and which is the client?
>
> You can see that the load from WireGuard encryption is about 42-43% per
> each
> core. But the thing is, one of them (the 1st) also gets to process
> interrupt
> load from the NIC, and that consumes the rest of it, causing the
> bottleneck. In
> theory, if you could limit WG to run encryption on all cores EXCEPT the
> first
> one, then maaaaybe...
>
>
With taskset you should be able to:
https://www.howtoforge.com/linux-taskset-command/


-- 
May the most significant bit of your life be positive.

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Re: Speed on Raspberry Pi 4

[Roman Mamedov]

On Thu, 18 Jul 2019 08:38:54 +0200
Janne Johansson <icepic.dz@gmail.com> wrote:

> With taskset you should be able to:
> https://www.howtoforge.com/linux-taskset-command/

It appears "taskset" only works on regular programs, not kernel threads:

# taskset -p -c 1 2128
pid 2128's current affinity list: 0
taskset: failed to set pid 2128's affinity: Invalid argument

# taskset -p -c 1 2129
pid 2129's current affinity list: 1
taskset: failed to set pid 2129's affinity: Invalid argument

As the above shows, WG threads are already bound to a particular CPU and this
can't be changed.

-- 
With respect,
Roman
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Re: Speed on Raspberry Pi 4

[Janne Johansson]

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Den tors 18 juli 2019 kl 08:56 skrev Roman Mamedov <rm@romanrm.net>:

> On Thu, 18 Jul 2019 08:38:54 +0200
> Janne Johansson <icepic.dz@gmail.com> wrote:
>
> > With taskset you should be able to:
> > https://www.howtoforge.com/linux-taskset-command/
>
> It appears "taskset" only works on regular programs, not kernel threads:
>
> # taskset -p -c 1 2128
> pid 2128's current affinity list: 0
> taskset: failed to set pid 2128's affinity: Invalid argument
>
> # taskset -p -c 1 2129
> pid 2129's current affinity list: 1
> taskset: failed to set pid 2129's affinity: Invalid argument
>
> As the above shows, WG threads are already bound to a particular CPU and
> this
> can't be changed.
>

Right, my bad.

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Re: Speed on Raspberry Pi 4

[Matthias Urlichs]

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Hi,
>
>     As the above shows, WG threads are already bound to a particular
>     CPU and this
>     can't be changed.
>
>
> Right, my bad. 

OK. So we have N kernel threads (one per CPU) and one CPU that really
shouldn't do anything but interrupt processing.

That looks like we need an option to limit wireguard to a specific set
of CPUs. That'd be a good option to have in any case, because we don't
want the poor Raspberry Pi (or any other semi-underpowered machine) to
starve everything else when it gets flooded with more wireguard work
than it can handle.

We could then set the network interface's IRQ affinity to one of the
"free" CPUs, and we'd be all set.

-- 
-- mit freundlichen Grüßen
-- 
-- Matthias Urlichs


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