Re: Network I/O performance

[Herbert Xu <herbert@gondor.apana.org.au>]

On Mon, May 18, 2009 at 12:14:34AM +0300, Avi Kivity wrote:
>
>> No, I am measuring UDP throughput performance. I have now tried using a 
>> different NIC model, and the e1000 model seems to achieve slightly 
>> better performance (CPU goes up to 110% only though). I have also been 
>> running virtio now, and while its performance with 2.6.20 was very poor 
>> too, when changing the guest kernel to 2.6.30, I get a reasonable 
>> performance and higher CPU utilization (e.g. it goes up to 180-190%). I 
>> have to throttle the incoming bandwidth though, because as soon as I go 
>> over a certain threshold, CPU goes back down to 90% and throughput goes 
>> down too.   
>
> Yes, there's a known issue with UDP, where we don't report congestion  
> and the queues start dropping packets.  There's a patch for tun queued  
> for the next merge window; you'll need a 2.6.31 host for that IIRC  
> (Herbert?)

It should be in 2.6.30 in fact.  However, this is for outbound
traffic only since inbound traffic shouldn't have this problem
of the guest sending faster than the wire.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
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