Re: Xen & I/O in clusters - problems! New Information

[Håvard Bjerke <Havard.Bjerke@idi.ntnu.no>]

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On Wed, Oct 27, 2004 at 07:26:10PM +0100, Ian Pratt wrote:
> > On Fri, Oct 22, 2004 at 06:47:35PM +0100, Ian Pratt wrote:
> > > > 
> > > > We tried to compile xen0 with CONFIG_E1000_NAPI = y and got the samre 
> > > > results between
> > > > two xen dom0 nodes. I am not sure if these interrupts tells anything:
> > > 
> > > It's the different rate at which the eth0 interrupt counts go up
> > > during your bandwidth tests that is interesting. e.g. poll it
> > > once a second during the test.
> > > 
> > 
> > We tried sending 1 MB and measured:
> 
> 1MB isn't really very much with a 128KB socket buffer. Do you get
> the same results with larger transfers?
> 

With 10 MB transfers the results are roughly the same:

native Linux with compiled-in SMP support, single CPU:
	~ 1365k interrupts
	114 kB/s
Xen0 with "nosmp":
	~ 1676 k interrupts
	76 kB/s

> > non-SMP native Linux:
> > 	~ 130k interrupts
> > 	114 kB/s
> > native Linux with compiled-in SMP support, single CPU:
> > 	~ 140k interrupts
> > 	114 kB/s
> > Xen0:
> > 	~ 180k interrupts
> > 	80 kB/s
> 
> It's pretty odd that Xen's taking more interrupts. Are you using
> the same native kernel version as you are for Xen?
> 

Yes, both are 2.4.27

> Also, what happens if you boot xen with 'nosmp' on the Xen
> command line.
> 

There seems to be no change in behaviour. The interrupt layout and count remains roughly the same.

Do you have any more tips? :)


Håvard


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