[announce] KVM/NET, paravirtual network device

[announce] KVM/NET, paravirtual network device

[Ingo Molnar]

here's a quick update wrt. the KVM paravirtualization work: i'm 
currently working on KVM/NET, which is a Linux<->Linux virtual network 
device driver between the KVM host and the KVM guest. It uses the new 
KVM-paravirtualization infrastructure that i've sent to this list 
yesterday.

while the code is still a prototype, it's working already and here are 
some early TCP bandwidth (bw_tcp from guest to host) performance results 
which i'm sure you'll enjoy:

  -----------------------------------------------------------
  | Native via loopback (mtu=1500)         :  235.57 MB/sec |
  | Native via loopback (mtu=4000)         :  487.12 MB/sec |
  -----------------------------------------------------------
  | Qemu via RTL-8029 emulation            :    2.84 MB/sec |
  | KVM via RTL-8029 emulation             :    7.41 MB/sec |
  -----------------------------------------------------------
  | KVM-para via KVM/NET device (mtu=1500) :  303.35 MB/sec |
  | KVM-para via KVM/NET device (mtu=4000) :  389.47 MB/sec |
  -----------------------------------------------------------

	Ingo

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Re: [announce] KVM/NET, paravirtual network device

[Rusty Russell]

On Thu, 2007-01-11 at 01:10 +0100, Ingo Molnar wrote:
> here's a quick update wrt. the KVM paravirtualization work: i'm 
> currently working on KVM/NET, which is a Linux<->Linux virtual network 
> device driver between the KVM host and the KVM guest. It uses the new 
> KVM-paravirtualization infrastructure that i've sent to this list 
> yesterday.
> 
> while the code is still a prototype, it's working already and here are 
> some early TCP bandwidth (bw_tcp from guest to host) performance results 
> which i'm sure you'll enjoy:

I assume you use kernel support in the host as well?  This is exactly
the code we should share, IMHO; Xen already has such a thing, and I'd
prefer not to have three implementations in the kernel....

Patches?
Rusty.



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Re: [announce] KVM/NET, paravirtual network device

[Ingo Molnar]

* Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org> wrote:

> On Thu, 2007-01-11 at 01:10 +0100, Ingo Molnar wrote:
> > here's a quick update wrt. the KVM paravirtualization work: i'm 
> > currently working on KVM/NET, which is a Linux<->Linux virtual network 
> > device driver between the KVM host and the KVM guest. It uses the new 
> > KVM-paravirtualization infrastructure that i've sent to this list 
> > yesterday.
> > 
> > while the code is still a prototype, it's working already and here are 
> > some early TCP bandwidth (bw_tcp from guest to host) performance results 
> > which i'm sure you'll enjoy:
> 
> I assume you use kernel support in the host as well?  This is exactly 
> the code we should share, IMHO; Xen already has such a thing, and I'd 
> prefer not to have three implementations in the kernel....
> 
> Patches?

no patches yet - it's still prototype. I hope to have something to look 
at tomorrow-ish. With lhype sharing ought to be possible, while Xen's 
model is quite different. I agree that we dont want 3 implementations in 
the kernel ...

	Ingo

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Re: [announce] KVM/NET, paravirtual network device

[Avi Kivity]

Ingo Molnar wrote:
> here's a quick update wrt. the KVM paravirtualization work: i'm 
> currently working on KVM/NET, which is a Linux<->Linux virtual network 
> device driver between the KVM host and the KVM guest. It uses the new 
> KVM-paravirtualization infrastructure that i've sent to this list 
> yesterday.
>
> while the code is still a prototype, it's working already and here are 
> some early TCP bandwidth (bw_tcp from guest to host) performance results 
> which i'm sure you'll enjoy:
>
>   -----------------------------------------------------------
>   | Native via loopback (mtu=1500)         :  235.57 MB/sec |
>   | Native via loopback (mtu=4000)         :  487.12 MB/sec |
>   -----------------------------------------------------------
>   | Qemu via RTL-8029 emulation            :    2.84 MB/sec |
>   | KVM via RTL-8029 emulation             :    7.41 MB/sec |
>   -----------------------------------------------------------
>   | KVM-para via KVM/NET device (mtu=1500) :  303.35 MB/sec |
>   | KVM-para via KVM/NET device (mtu=4000) :  389.47 MB/sec |
>   -----------------------------------------------------------
>
>   

That's about a 5000% improvement :)

Amazing, both the bandwidth results and the speed in which it was 
reached.  I'm really at a loss for words.


-- 
error compiling committee.c: too many arguments to function


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Re: [announce] KVM/NET, paravirtual network device

[Dor Laor]

>On Thu, 2007-01-11 at 01:10 +0100, Ingo Molnar wrote:
>> here's a quick update wrt. the KVM paravirtualization work: i'm
>> currently working on KVM/NET, which is a Linux<->Linux virtual
network
>> device driver between the KVM host and the KVM guest. It uses the new
>> KVM-paravirtualization infrastructure that i've sent to this list
>> yesterday.
>>
>> while the code is still a prototype, it's working already and here
are
>> some early TCP bandwidth (bw_tcp from guest to host) performance
results
>> which i'm sure you'll enjoy:
>
>I assume you use kernel support in the host as well?  This is exactly
>the code we should share, IMHO; Xen already has such a thing, and I'd
>prefer not to have three implementations in the kernel....

Well, Xen implementation has the grant tables and all their ring code (a
good one thought). On the beginning you can start without convergence
and aim towards it. Here is a link that describes Xen HVM pv driver
performance:
http://www.xensource.com/files/summit_3/xen-pv-drivers.pdf
for 1500 mtu their doing 400Mbs rx, 500+Mbs tx. I guess Ingo will soon
reach that...

>
>Patches?
>Rusty.

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Re: [announce] KVM/NET, paravirtual network device

[Andy Ross]

Avi Kivity wrote:
 > Ingo Molnar wrote:
 > >   | Qemu via RTL-8029 emulation            :    2.84 MB/sec |
 > >   | KVM via RTL-8029 emulation             :    7.41 MB/sec |
 > >   | KVM-para via KVM/NET device (mtu=1500) :  303.35 MB/sec |
 >
 > That's about a 5000% improvement :)
 >
 > Amazing, both the bandwidth results and the speed in which it was
 > reached.  I'm really at a loss for words.

Is maybe a better question to ask what it is that makes the Qemu
hardware emulation so slow?

Andy

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Re: [announce] KVM/NET, paravirtual network device

[Avi Kivity]

Andy Ross wrote:
> Avi Kivity wrote:
>  > Ingo Molnar wrote:
>  > >   | Qemu via RTL-8029 emulation            :    2.84 MB/sec |
>  > >   | KVM via RTL-8029 emulation             :    7.41 MB/sec |
>  > >   | KVM-para via KVM/NET device (mtu=1500) :  303.35 MB/sec |
>  >
>  > That's about a 5000% improvement :)
>  >
>  > Amazing, both the bandwidth results and the speed in which it was
>  > reached.  I'm really at a loss for words.
>
> Is maybe a better question to ask what it is that makes the Qemu
> hardware emulation so slow?
>   

To send a packet through ne2k, you need about 44 pio writes. at ~10us 
per pio write, that's about 2k packets/sec, or 3MB/sec.  RTL8029 is 
about twice as fast.

A pv interface can send multiple packets per hypercall.  Working 
backward from Ingo's numbers, 300 MB/sec = 200k packets/sec = 2 
packets/hypercall.  Or perhaps his hardware is faster and he does 1 
packet/hypercall.  Or maybe I need to take the memcpy time into account 
at this bandwidth :)

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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