[linux-fai] why does "yes" take so much cpu time?

[Thomas Gebhardt]

Hi,

when snooping around at a client installation I found that
during the software installation most of the time "apt-get"
and "yes" took about 66% / 33% of the cpu time:

# top
 11:48am  up 1 min,  0 users,  load average: 1.10, 0.38, 0.13                  

CPU states: 24.7% user, 75.2% system,  0.0% nice,  0.0% idle
Mem:  127808K av, 122756K used,   5052K free,   7760K shrd,  92656K buff
Swap:      0K av,      0K used,      0K free                 15592K cached
 
  PID USER     PRI  NI  SIZE  RSS SHARE STAT  LIB %CPU %MEM   TIME COMMAND
  267 root      14   0  2912 2912  2880 R       0 63.0  2.2   0:10 apt-get
  252 root       7   0   364  364   304 S       0 36.5  0.2   0:05 yes      
  ...

# ps fax (some processes omitted)
    7 ?        SW     0:00 [rpciod]
    8 tty1     S      0:00 init boot
    9 tty1     S      0:00  \_ bash /etc/init.d/rcS
   11 tty1     S      0:00      \_ cat /proc/kmsg
   81 tty1     S      0:00      \_ bash /etc/init.d/rcS
   82 tty1     S      0:00          \_ bash /etc/init.d/rcS
   83 tty1     S      0:00          |   \_ tee -a /tmp/rcS.log
  252 tty1     S      0:06          \_ yes n
  253 tty1     S      0:00          \_ perl /sbin/install_packages
  254 tty1     S      0:00              \_ apt-get -y --fix-missing install 
perl-base
  267 tty1     R      0:12                  \_ apt-get -y --fix-missing 
install perl-base
   48 ?        S      0:00 /usr/sbin/sshd                                      


1. I do not know why this happens (any idea?) Do yes and apt-get play
   pingpong together (until some timeout ends the game)? When I do
   not install perl-base and run 
   "apt-get -y --fix-missing install perl-base" manually
   after installation, everything seems to work quick and fine.

2. Can anyone reproduce this?

3. Could one avoid this? If yes, would installation speed up?

Kind regards, Thomas