disk encryption performance hit

[Jeff Bastian]

On Fri, 16 May 2008, Gordon Messmer wrote:
> Jeff Bastian wrote:
>> I installed F9 yesterday under VMware Fusion 1.1.2 and enabled disk 
>> encryption.  It was working fine until cron fired up makewhatis.  At that 
>> point the system became so sluggish it was basically unusable.
>
> Try to reproduce that problem on real hardware rather than VMWare.  The key 
> repeat thing used to bug me a lot, but I thought Michal Maruska fixed it 
> years ago:
> https://bugzilla.redhat.com/show_bug.cgi?id=76959



Before jumping to bare metal, I created a new VMware machine and installed 
F9 -- but without disk encryption -- and repeated the test.  I made sure 
the installed packages were the same on both of my virtual machines, and 
enabled VMI, and used 'elevator=noop' on both.

On the new virtual machine, I got similar results with 'time 
/etc/cron.weekly/makewhatis.cron':
    # time /etc/cron.weekly/makewhatis.cron

    real    35m26.437s
    user    3m12.721s
    sys     13m6.747s

And, according to 'top', the CPU was spending 80%+ on the system.  (Under 
Fedora 8, it stays around 45%.)

I'm also seeing the missing & repeated key stroke behavior while 
makewhatis is running.

So, it would seem that the disk encryption is NOT to blame for the 
sluggish behavior.  There's something else going on, maybe because it's a 
virtual machine, or maybe with the SCSI drivers in the latest kernel.

It could be because current VMware Tools does not install cleanly on 
2.6.24 and newer kernels.  I know there are some unofficial patches to get 
it to compile, but I haven't tried them yet.  On my F8 virtual machine, 
I'm still using a 2.6.23 kernel since the tools installed fine with it.

Hmmm, time to do some more experiments...

Jeff