[Trac #939] Can save much memory by running a simple display manager

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#939: Can save much memory by running a simple display manager
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 Reporter:  jg               |        Owner:  cjb    
     Type:  defect           |       Status:  new    
 Priority:  high             |    Milestone:  BTest-3
Component:  x window system  |   Resolution:         
 Keywords:                   |  
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Comment (by AlbertCahalan):

 According to /proc/*/smaps, the shell scripts have 732 KB of dirty data in
 RAM. (684 KB of Private_Dirty, plus 96 KB of Shared_Dirty data with 2-way
 sharing)

 You can do tail-call optimization on the shell scripts via exec. Fixes:

 In /usr/local/bin/dm, put "exec " at the beginning of the line that starts
 with su. Delete the next (last) line, with the sleep. If the sleep is
 truly required, put it up front in some sort of "if" block, but I'll guess
 that the sleep is merely a hack to let a fast typist get into runlevel 1.
 Getting into runlevel 1 is easier via a reboot, and the sleep prevents
 using exec.

 Also in /usr/local/bin/dm, change the /usr/local/bin/dm-unpriv invocation
 to /usr/bin/startx. (alternately modify /usr/local/bin/dm-unpriv to do an
 exec, but running a near-empty script is pointless)

 In /usr/bin/startx, add "exec " to the beginning of the line that starts
 with "xinit ". The commands below should get moved to the top of the file.
 While they are logically "clean-up operations", and thus to be done at the
 end, it is perfectly fine to do that clean-up when next starting the X
 server.

 The su program may need modification. The su command probably hangs around
 for some authentication systems that might need a clean-up; this is not
 useful here.

 Unless I missed something, the end result should be that xinit is a child
 of init and 732 KB of RAM is recovered.

-- 
Ticket URL: <http://dev.laptop.org/ticket/939#comment:4>
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