On Sat, Dec 03, 2005 at 10:57:08AM -0500, Warren Baird wrote:
> BandiPat wrote:
> >
> >It's simple, Apple strangles the Unix that is on the machine.  If you 
> >had a straight install of Unix without anything Apple over or under it, 
> >you would see a dramatic increase in speed also.
> >
> >I read an article a few months ago about the problems associated with OS 
> >X on their machines.  I wish I could remember where it was, so I could 
> >point you to it.  It's just Apple's way of taking something really good 
> >and making it less than perfect with their add ons.  Every user I've 
> >talked to or article I've read remarks how much faster Linux is on the 
> >PPC than OS X.  It's a great cpu, sadly Apple didn't want it to appear 
> >that way.
> Hmm.   I did see an article a while back talking about perf issues with 
> apache --- I think it had something to do with context switches taking 
> longer than on linux...   But that shouldn't affect the Gimp much...

Actually, it would effect GIMP, and is the most probable reason why GIMP
on Linux is so much faster on the same hardware. Plug-ins run as
separate processes, but as they run they talk to the main app quite a
bit, to get/put data, as well as calling image manipulation functions.
So there's a ton of context switching involved, which hurts you badly on
OS X. I/O is also much much slower compared to Linux.

Note I haven't actually profiled anything on OS X, but the poor context
switch performance is the first thing I thought of when I read your
earlier mails.

> And I'm not sure I buy the argument that Mac OS X is just slower --- 
> like I said, photoshop was about 15 times faster that the Gimp at doing 
> an unsharp mask on an 800 mhz g4 on mac os x.

Photoshop's plugins are not run as separate processes, so they aren't
affected by context switch performance. Unsharp mask in photoshop might
not even be implemented as a plugin even. Also, I bet they're taking
advantage of Altivec there. And like someone else in this thread said,
they may be also precomputing the result.

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