Slow memory

[bartcramer]

Hi all,

I am having the following problem: when I run intensive tasks on my guest, that release and consume much memory, the whole process tend to get very slow after a while, by a factor of 4 or 5, sometimes. However, initially, it works fine.

Some more detail:

• I am running a fairly recent MacBook, with 4GB, on Leopard, with Ubuntu-JeOS 8.10 as guest. 3 GB of memory is devoted to the guest. I am using Fusion 2.0.3.

• The tasks I am performing are mostly Lisp. It seems that other processes in C/C++ do not suffer from this problem.

• The slowdown seems to be at the system level, not at the application level. Some simple parts of the algorithm can take minutes.

• No swapping is going on

• Shutting down the virtual machine is extremely slow after such computation. It might take up to 2 or 3 minutes, even after the X window system has shut down.

• The behaviour is consistent and reproducible.

My initial thought is that the memory is fragmented, and that the system does on-demand defragging or reclaiming. But that is just a guess.

Anhbody an idea?

[admin]

Check whether Fusion is set to optimize for guest disk performance or host application performance. This affects OS X's settings for disk caching, and toggling this setting (I think you need to shut down/suspend the virtual machine, and possibly restart Fusion) may help.

[bartcramer]

Thanks for the suggestion. I had it already on Optimize for guest OS,

which seems to be the most appropriate...

[admin]

Thanks for the suggestion. I had it already on Optimize for guest OS,

which seems to be the most appropriate...

Try switching it anyway, the tradeoff between which one to favor is sometimes counterintuitive. OS X might be favoring caching the guest disk (not the overall guest) to the point where host applications (such as Fusion) are affected. If Fusion is swapped out, it doesn't matter that the guest disk is nicely cached.