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[Bug 1259861] Re: 5-10 second delay in kernel boot


I have been seeing this on multiple machines since trusty (at least).
I'm currently running wily.

I noticed that if I remove the 'ip=dhcp' kernel command line parameter
then the 10 second delay goes away.  (I added ip=dhcp so that I could
ssh into the initramfs to unlock the encrypted root device from remote.)
I'm not sure why 'ip=dhcp' causes that delay.  I was able to rule out
the initramfs—I modified /usr/share/initramfs-tools/init to print the
contents of /proc/uptime as early as possible.  According to the logged
time, init doesn't start running until after the 10 second pause (unless
mounting /proc takes 10 seconds when ip=dhcp is in the command line
arguments, which I doubt).

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  5-10 second delay in kernel boot

Status in linux package in Ubuntu:

Bug description:
  In Trusty I see a big delay while the kernel boots that I did not see back in Precise.
  Some people have been experiencing this in Saucy too, so I don't know exactly when it started happening.
  Excerpt from dmesg:
  [    3.740100] Switched to clocksource tsc
  [   14.208118] PM: Hibernation image not present or could not be loaded.
  [   14.208885] Freeing unused kernel memory: 864K (c19ac000 - c1a84000)

  The exact messages above don't matter, they are different on different boots or on different machines.
  It even happens with e.g. 
  $ sudo kvm -m 768 -cdrom trusty-desktop-i386.iso

  My current kernel is
  Linux server 3.12.0-7-generic #15-Ubuntu SMP Sun Dec 8 23:42:09 UTC 2013 i686 i686 i686 GNU/Linux
  ...but the exact version, maybe from 3.8 to 3.12+, shouldn't matter, just run `dmesg` yourself and check if there's a big delay there.

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