[Vm-dev] Making a Slower VM

David T. Lewis lewis at mail.msen.com
Sun Feb 9 19:46:14 UTC 2014


On Sun, Feb 09, 2014 at 10:23:37AM -0800, tim Rowledge wrote:
> 
> 
> On 09-02-2014, at 10:07 AM, David T. Lewis <lewis at mail.msen.com> wrote:
> > Joking aside, there actually is one legitimate reason for wanting a slow VM.
> > With high performance VMs and with ever faster hardware, it is very easy to
> > implement sloppy things in the image that go unnoticed until someone runs the
> > image on an old machine or on limited hardware. It is sometimes useful to
> > test on old hardware or on a slow VM to check for this.
> 
> The cheapest and easiest way to do it these days is to buy a Raspberry Pi. You?ll learn very quickly where you have used crappy algorithms or poor technique? though of course you do have to put up with X windows as well. Unless you try RISC OS, which although not able to make the raw compute performance faster at least has a window system that doesn?t send every pixel to the screen via Deep Space Network to the relay on Sedna.
> 
> > I think someone mentioned it earlier, but a very easy way to produce an
> > intentionally slow VM is to generate the sources from VMMaker with the
> > inlining step disabled. The slang inliner is extremely effective, and turning
> > it off produces impressively sluggish results.
> 
> Does that actually work these days? Last I remember was that turning inlining off wouldn?t produce a buildable interp.c file. If someone has had the patience to make it work then I?m impressed.
> 

Dang it, you're right, it's not working. I guess I have not tried this in
a while, though I know that it used to work. Making things go slower seems
like a worthwhile thing to do on a Sunday afternoon, so I think I'll see
if I can fix it.

Dave
 


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