Re: [Xen-users] Serious performance problems - is Xen not ready for production use?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I hope my current problems with Xen 2.0.5 are related to my own
> stupidity - otherwise I'm getting the impression that Xen is not ready
> for productional use at the current stage.

It's a project that's still evolving rapidly - particularly in terms of the 
installation and management toolkit - however lots of people are using it in 
production settings already.  The community sites at xensource.com run in Xen 
domains, so we do eat our own dogfood :-)

Performance is one of Xen's key focus points.  Rest assured that the problems 
you're seeing are not normal - hopefully we can get you up and running.

> Everything seems to work - all services are there and working so the
> system itself is working ok. But: when accessing resources like squirrel
> webmail or accessing the IMAP service the machine is very slow (compared
> to old setup). The load average climbs easily to values above 6, 12 was
> the highest value that I got when playing with a single client. Old
> system was never used in a way that a lot CPU power was needed, load avg
> stays there normally below 0.05-0.1 -- on the Xen setup the load never
> dropped below 2.5 (!!).

First check: Can you verify that IDE DMA is working on your system?  If not, 
you'll probably need to build a new kernel with the appropriate drivers.

If that doesn't help:
* what sort of workload are you imposing in your tests?
* do you know where the CPU time is going in the domain?
* does the output of top and vmstat look weird?
* anything strange in the dmesg output (try comparing to the dmesg from a 
native boot)?

> Together with the still unsolved question about ballooning the memory
> this caused my impression that I shouldn't use Xen in production
> environment (see also my message from 06/28/2005 03:47 'Can't increase
> memory size during runtime' or 'problem to balloon memory beyond initial
> allocation' from Xuehai Zhang (07/07/2005 06:30). This is really sad
> because I really like Xen and WOULD like to use it...

The memory ballooning needs to be fixed.  I can't remember what release the 
reported breakage was in - it's probably an easy fix either way.  The break 
probably went unnoticed because people usually don't balloon domains above 
their initial allocation.

HTH,
Mark

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