• Leigh B. Stoller's avatar
    A set of small performance related changes that I made after putting · 38fa67c4
    Leigh B. Stoller authored
    in the timestamps, and seeing what was taking so much time.
    
    * Increase the overlap from two to four seconds (have vnodesetup exit
      earlier) so that the next jail can start sooner. Using getrusage it
      seemed pretty clear that there were plenty of cycles available to
      start the next jail going a little earlier. Instead of looking for
      the watchdog pid file to appear, I touch (in mkjail) a specific file
      in the jail directory , and have vnodesetup look for that file
      instead of the pid.
    
    * Cut back the number of inodes in the filesystem! Sheesh, we ere
      creating 137,000 inodes for a 50MB vnode filesystem. Takes 1
      second to do that. Reduced to 30,000 and the time when to .1
      seconds. Could probably go even lower.
    
    * Add -p option to fsck when restoring a jail from an existing
      filesystem. No need to force check the filesystem if its clean.
    
    * Instead of running MAKDEV inside each jail filesystem (which was
      also taking .8 seconds to do), do it just once and stash a copy in
      /var/emulab/jails. Each jail does a "hier cp" of that master copy
      into the jail filesystem. Reduced the time to .05 seconds.
    
    So, for the results:
    
    Original time to boot a jail: 8.2 seconds, with the last two seconds
    overlapped with the next one.
    
    Original time to reinstate a jail after halting it (filesystem left
    behind): 6.5 seconds, with the last 1.5 seconds overlapped with the next
    one.
    
    Original time to boot 16 jails on a pc850: 2 minutes and 12 seconds.
    
    ---------------------------------------------------------------------------
    
    New time to boot a jail: 6.2 seconds, with the last 4 seconds overlapped
    with the next one.
    
    New time to reinstate a jail after halting it: 6 seconds, with the last 4
    seconds overlapped with the next onw.
    
    New time to boot 16 jails on a pc850: 88 seconds. Does this number ring any
    bells? :-)
    38fa67c4