# VMWare Causing Huge IOWait Times [Solved]

## mhornnt

Just had to decrease the memory allocated to the virtual machine to eliminate spillover into swap space that was causin the disk access and jump in IOWait

I've finally started to play around with vmware for the couple of apps I typically still booted into a native windows install to use. The problem is, anytime vmware is running, IOWait times jump to near 100% and the useability of my computer grinds to a halt. The first thing I checked was that DMA was properly enabled which it is, both in the kernel as well as with hdparm. Now, I am running this on a laptop, so I understand that hd performance won't be as high as with say a desktop, but even simple things like windows loading and logging in will bring the IOWait to near 100% for 15 to 20 minutes. Also, I'm using VMPlayer, so could the performance issue be resolved if instead I tried Workstation or maybe the server? I figured I'd try the player as the apps I need to run aren't all that intensive and I thought the player would be the simplest solution with the least overhead. Any suggestions to clear this up would be greatly appreciated, becaused I'd love to completely rid myself of the native windows install on this computer.Last edited by mhornnt on Tue Jun 13, 2006 1:55 am; edited 1 time in total

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## Headrush

What are the specs for your system, especially the amount of RAM?

Did you install vmware-tools inside the virtual machine?

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## mhornnt

My system is a 1.6Ghz pentium m, 1 gig of ram, an nvidia geforce 4200 go card, and the hd is 60gig 5400rpm. I haven't installed vmware-tools. By inside the virtual machine, i take it you mean that within the virtual windows environment to download and install the vmware-tools? 

Also, I've noticed since my first post that dmesg reports numerous lines like the following:

/dev/vmmon[8401]: host clock rate change request 1043 -> 83

/dev/vmmon[8401]: host clock rate change request 83 -> 19

/dev/vmmon[8401]: host clock rate change request 19 -> 1

/dev/vmmon[8401]: host clock rate change request 1 -> 19

/dev/vmmon[8401]: host clock rate change request 19 -> 83

/dev/vmmon[8401]: host clock rate change request 83 -> 1043

/dev/vmmon[8401]: /dev/rtc open failed: -19

Not sure if these are at all related or not

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## jschellhaass

From the last line you posted I would say you do not have rtc in the kernel.

Device Drivers -> Character Devices -> Enhanced Realtime Clock Support.

I'm not certain how this will effect the IO wait times.  

Vmware at one time required rtc support.

jeff

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## mhornnt

Turns out, after using the setup a bit more, that with anything more than one simple app running the slowdown gets to be great enough as to make most things essentially unusable. So any more ideas would be great

Ok, adding rtc did take care of the error in dmesg, but didnt seem to have an effect on the performance at all. I installed vmware-tools, and while IOWait still jumps to near 100%, the actually performance is much better, and except for a bit of lag when first starting programs, and windows being a bit slow to load initially, is very acceptable. I'm not really familiar with vmware-tools and exactly what it does. Playing with it briefly it seems pretty limited in its options, but since installing it like i said the performance is much better so it must be doing something.

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## bollucks

IO wait means you have lots of disk activity. You're probably hitting swap which is easy to do with two full operating systems running.

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## mhornnt

Good call bollucks. Its been so long since I've had enough things goin to tap into my swap space I didn't even think to look at that. I've lowered the amount of memory the virtual machine is using, and the need for swap has been eliminated once again. The lag in both windows startup and loading and running of windows apps has dropped and the huge IOWait levels seeem to have disappeared.

Thanks

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## ck42

 *mhornnt wrote:*   

> Good call bollucks. Its been so long since I've had enough things goin to tap into my swap space I didn't even think to look at that. I've lowered the amount of memory the virtual machine is using, and the need for swap has been eliminated once again. The lag in both windows startup and loading and running of windows apps has dropped and the huge IOWait levels seeem to have disappeared.
> 
> Thanks

 

mrhornnt,

I think I'm currently dealing with something identical and wanted to clarify something.

First, my VMware system is running XP with a full gig of RAM provided to the virtual OS.  I've also verified DMA settings (says UDMA2??) and have turned off pretty much all eye candy on the XP system.

Like you had mentioned, if I try to run more than a single app at a time in XP, my entire Gentoo/XP system pretty much becomes unusable.  On the XP system, I hear the drive grinding away for long periods of times after starting just about any application.  It's painful.  It wouldn't be so bad if it wasn't affecting my Gentoo system as well.

So....you mentioned that you "lowered the amount of memory the virtual machine is using" and this appears to have resolved the problem.  Can you clarify exactly WHAT you lowered?  Did you lower the amount of memory given to VMware for the XP install?  Did you reduce the pagefile size for XP?   Something else?

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