Re: Interesting performance quirk.

[Jeffrey Creem <jeff@thecreems.com>]

Peter C. Chapin wrote:

> Now the interesting part. My main development system is a Windows XP
> laptop. On this system my "optimized" Blowfish benchmark encrypts or
> decrypts at about 11 MB/s (curiously decryption is a little faster than
> encryption, which seems odd). It also happens that I have OpenSUSE 10.2
> Linux running on the same box in a VMware virtual machine. In that
> environment my benchmark encrypts or decrypts at fully 27 MB/s. It's
> over twice as fast! I'm using GNAT GPL 2008 in both cases with the same
> compiler options and exactly the same source code. I'm even using the
> same basic hardware although, as I said, one of my systems---the faster
> one---is a virtual machine.
> 

Hmm, certainly seems odd. I wonder if one of these two versions was 
configured differently and thus has a different set of default options.

It seems like it would be interesting to quickly disassembly the inner 
loop on the two machines and see if anything jumps out. From the 
description, it seems like you should be getting identical code.

Or maybe you just need to keep nesting the VMs until this code runs at 
200 GB/sec :)