[Radiance-general] No more Mr. Nice Guy

[atelier iebele abel]

He Greg,

I just have a G5 for editing video my last project, and I was surprised 
how well a G5 is rendering with rpict. The G5 was one of the best 
workhorses this month!!
On my G5 the deafult processor performance is already set on  "Highest".
Besides that, removing the -DNICE= arguments in rt/ Rmakefile is 
something I like to check out, but I am fearly new with OSX, and I 
haven't found any development tools yet.
Where do I find development tools for OSX, so I can run make?

-Iebele



Greg Ward wrote:

> Hi All,
>
> This message is most relevant to Mac users, but introduces a change  
> that may affect rpict and rtrace performance in future releases on  
> all platforms.  Specifically, I have taken out the NICE= macro  
> settings from the Rmakefile in src/rt, so future builds will run all  
> Radiance programs at the standard user priority.
>
> I made a fortuitous discovery whilst playing around with the very  
> cool (no pun intended) TemperatureMonitor freeware <http:// 
> www.bresink.com/osx/TemperatureMonitor.html> on my new PowerMac G5  
> quad.  It's lots of fun to watch the processor temps go up and down  
> with load.  The funny thing I noticed was that changing the Energy  
> Savings settings had an unexpected effect on temperatures, which are  
> in turn related to power consumption and (presumably) processor  
> performance.
>
> The Energy Saver options lists three processor performance settings,  
> "Highest," "Automatic," and "Reduced."  With the machine idle, there  
> were only slight differences between the three; I had expected to see  
> more, especially on the "Highest" setting...  The biggest difference  
> was between "Highest" and "Reduced" with all four processors busy,  
> and that was no surprise.  What was a surprise was that when I had  
> four rpict jobs going in parallel, there was a big difference between  
> the temperatures using the "Highest" versus "Automatic" settings.   
> Apple documentation states that the performance penalty for using  
> "Automatic" should be very small, so I figured the temperature change  
> would also be small.  That's when I decided to measure actual  
> performance.
>
> What a difference!  Between the "Highest" and "Automatic" settings, I  
> noticed a performance difference of over 60%, where I expected to see  
> little or none.  What I did expect was a performance hit moving to  
> the "Reduced" setting, which indeed there was, but it was only  
> another 13% worse than "Automatic."  This really seemed wrong to me.   
> That's when I decided to start playing around with the "nice" level  
> of rpict.
>
> The "nice" setting on a process is a way to tell Unix that a job is  
> not a top priority, and interactive processes should be given more of  
> the CPU if there are any running.  However, in the past, it hasn't  
> much affected the performance of a process if there are no other jobs  
> to contend with.  I put nice() calls in Radiance way back when multi- 
> user Unix's were the rule, and we had to peacefully coexist with a  
> lot of other people who might get annoyed if I hogged all the system  
> resources, as Radiance is wont to do.
>
> In short, I found out that removing the nice() system call from rpict  
> achieved the "Highest" performance figure even when the Energy Saver  
> processor speed was set to "Automatic."  (The "Reduced" performance  
> was not affected.)  Apparently, Mac OS X 10.4 (at least) uses the  
> process "nice" setting to decide whether or not to kick the CPU speed  
> up a notch.  This might be a new feature of the OS, as I don't have  
> access to a maching running Jaguar or Panther to try it there.
>
> The bottom line in all this is that if you own a Mac and you're  
> running Radiance on it, be sure to use the "Highest" setting in the  
> Energy Saver control panel, because if you don't, your rendering  
> might just be running 60% slower than you would like it to.  Option B  
> is to remove the -DNICE= arguments from the build lines in src/rt/ 
> Rmakefile and remove the affected object files (rpmain.o and  
> rtmain.o) then rerun "rmake install" in the rt directory.  Or,  
> download Saturday's HEAD release and build that.  (I think I'm too  
> late for tomorrow.)  Then, you can leave the processor performance on  
> "Automatic," which is the default for normal operation.
>
> I wish I had made this discovery a couple of years ago....
>
> -Greg
>
>
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