Re: [Xen-users] Transient xen performance issue

[Joel Richard <xen@xxxxxxxxxxxxxxx>]

Dan,

You didn't mention disk activity or whether the CPUs are waiting on  
anything. I have noticed (at least in my limited experience) that when  
a DomU is using a lot of disk, the Dom0 will show that the CPU (using  
plain old "top") is spending a significant amount of time waiting for  
the I/O.
Here's my top header. Note that this machine is mostly idle. :)

top - 15:41:57 up  5:59,  2 users,  load average: 0.00, 0.00, 0.00
Tasks:  98 total,   1 running,  97 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni, 99.7%id,  0.2%wa,  0.0%hi,   
0.0%si,  0.0%st
But if you have a lot in "wa" (I/O wait) that could be the source of  
some trouble.
In other words, if the server is not doing what you want it to be  
doing, you need to figure out what it IS doing. :)
--Joel


On Mar 9, 2009, at 10:49 PM, Dan Zhang wrote:

> I'm installing Xen with the OpenSUSE 10.2 distro and the  
> bigsmp-2.6.18.8-0.13.i586 kernel. However, I occasionally get insane  
> amounts of slowdown (almost 100x) in dom0. On bootup, performance is  
> normal. After an undeterministic period of time, I get this crazy  
> amount of slowdown. I'm not sure why this is the case and I have  
> spent a long time trying to figure it out. There are no background  
> processes running and nothing CPU intensive shows up on top or ps aux.
> One point of interest is that when I run 'lsmod', the modules  
> ide_core and ide_disk are missing. I tried installing them but it  
> seems that they aren't necessary. Since performance is fine on  
> startup, I'm not sure if this is a problem.
> I'm installing and compiling Xen 3.3.0 from scratch by using "make  
> world", etc.
> Does anyone have any ideas or suggestions?
>
> Thanks!
>
> Dan
>
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Joel Richard
The Richard Group
joel@xxxxxxxxxxxxxxxxx
703-584-5802




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