[ale] Using the VT capability of the CPU...

[Scott Castaline]

Michael B. Trausch wrote:
> On Sat, 2007-04-28 at 18:19 -0400, Michael B. Trausch wrote:
>> Also, there was a bit of a performance issue with the kernel losing 
>> interrupts, but I found a post somewhere on the 'net (don't have the 
>> bookmark handy, unfortunately) that said to enable RTC emulation in 
>> the kernel to fix it and gain a significant amount of performance.  I 
>> am about to try it to see if it works the way the site said it would, 
>> because I rebuilt the kernel and flipped that on.
> 
> Well.  I have mucked around with that and I am really impressed.  I 
> found the the post with the information I referenced earlier 
> <http://www.mail-archive.com/kvm-devel at lists.sourceforge.net/msg02285.html>, 
> so I there it is so that y'all can see it.
> 
> This does seem to significantly improve the performance, along with some 
> of the other modifications that I made to the kernel.  Specifically, I 
> enabled the low latency functionality and increased the timer frequency 
> from 250Hz to 1000Hz.  The sound from the Windows XP guest is no longer 
> clipping, and everything but the video performance is absolutely 
> amazing.  Of course, that means that I get better-than-QEMU performance 
> now, and that's wonderful.  Now if only QEMU would create a second 
> thread on SMP systems... :-)
> 
> There are a few other modifications, and the total difference from the 
> stock Ubuntu kernel is only 18 lines.  Basically, I made the kernel 
> fullly preemptive, reduced the number of supported processors to two 
> (since that's all that I have; theoretically this should reduce the 
> kernel's memory footprint, but I don't even know where to begin looking 
> for that type of information anymore...), enabled that RTC thing, and 
> made the kernel specific for AMD64 systems as opposed to generic support 
> for both EM64T and AMD64.  All in all, the difference is extremely 
> noticeable.
> 
> In case anyone is interested, I am attaching a gzip'd unified diff of 
> the configuration differences.  Perhaps someone will benefit from them, 
> or be able to tweak them further for their own use.
> 
>     -- Mike
> 
> --
> Michael B. Trausch 	
> fd0man at gmail.com <mailto:fd0man at gmail.com>
> Phone: (404) 592-5746 	
> Jabber IM: 	fd0man at gmail.com
> fd0man at livejournal.com
> 
> *Demand Freedom!  Use **/open/** and **/free/** protocols, standards, 
> and software!*
> 
> 
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In your stumbling around, you may want to check out VirtualBox. I 
haven't done it but you are supposed to be able to run multiple VMs on 
the same host. You can also go either way, M$ host, Linux guest, or the 
preferable way Linux host and M$ guest and the most preferred way Linux 
host Linux guest ;=)