Re: Serious performance problem with process output on Mac OSX

[Adrian Robert]

> When emacs is processing such output, there is a kind of lock up where
> it literally can take many seconds to switch desktops or to switch
> between applications (Cmd-TAB).


Hi,

I was able to reproduce this also on a 10.6.2 system, simply by executing the 
"ls -lR /System" command in a shell buffer and minimizing it.  What I noticed 
was that app switching through clicking on other app windows is as fast as 
normal when a disk-intensive background process is going on, but that Cmd-tab 
or clicking on the dock was slow.  Under Activity Monitor or top, the "Dock" 
process is taking up a lot of CPU.  This seems to have something to do with the 
updates Dock wants to do for the icon based on whatever methods Emacs is 
calling periodically.  I don't think it has to do with external processes -- 
but I couldn't figure out a way to get a growing buffer redisplayed while 
iconified purely from lisp code to test for sure.

Nor does it have to do purely with output -- the high Dock CPU usage occurs 
whether or not emacs is actually displaying the buffer doing the ls or not, and 
running the same ls -lR in Terminal and minimizing does not cause it.

I suspect unneeded calls to one of the icon/icon_type methods in nsfns.m or the 
miniwindowimage methods in nsterm.m are causing this.  Someone could try 
shortcircuiting these in the source and seeing if the problem still obtains.

It would also be interesting to know if this occurs under Leopard or Tiger, if 
anyone has access to those systems.

thanks,
Adrian