[Ti] slightly OT: which apps dual-processor aware?

[Chris Olson]

On Apr 12, 2005, at 9:35 PM, Ronald Woodland wrote:

> I have yet to see one of the CPUs idle while the other one is working. 
>  The numbers move around and often bounce back and forth as the 
> workload is distributed.  Dual processors working in beautiful 
> cooperation with the robustly stable and fluid Mac OS -- it gives me 
> goosebumps just thinking about it.

The Mach kernel does the thread scheduling for the cpu(s).  Mach does a 
very good job at SMP - it was designed for it.  Both Carbon and Cocoa 
applications can be multithreaded but Carbon will use Multiprocessing 
Services (as in Mac OS 9).  Cocoa uses the NSThread class with 
NSThread's detachNewThreadSelector:toTarget:withObject

Some applications like Safari will throttle the threads if one requires 
the other to be at a certain point before continuing by using condition 
locks (NSConditionLock).  But if an app uses a lot of condition locks 
or passes many objects and messages between threads, application 
performance can suffer.  Safari, by design, does not benefit from dual 
processors.  Neither does Mail, Sherlock, iCal, Finder, and most other 
every day applications and utilities.  Only cpu-intensive tasks and 
applications really take full advantage of it.  Because of OS X's 
pre-emptive multithreading capability, along with the Mach kernel's 
capability to schedule and switch threads many times per second on one 
cpu, you just don't notice the difference until the total system load 
on one cpu reaches 100% cpu time.
--
Chris