[Yaird-devel] Bug#391446: yaird: Free memory by nuking rootfs before switching root

[Peter Colberg]

Although it does not matter regarding the nuke_dir subject, the
"numbers" displayed above were not really suited to show the memory
usage of the initramfs.

Just to be nit-picky myself, here are the truly initramfs-relevant
/proc/meminfo cached memory numbers for ten successive boots with
init=/bin/dash, 5 without and 5 with the nuke_dir function enabled
in run_init.c.

without nuke_dir (two boots):
  Cached:           7016 kB		(Active:           5320 kB)
  Cached:           7016 kB		(Active:           5528 kB)
  Cached:           7016 kB		(Active:           5596 kB)
  Cached:           7016 kB		(Active:           5536 kB)
  Cached:           7016 kB		(Active:           5532 kB)

  $ gzip -d < /boot/initrd_without_nuke | cpio -t >/dev/null 
  10224 blocks

with nuke_dir (two boots):
  Cached:           1712 kB		(Active:           1204 kB)
  Cached:           1712 kB		(Active:           1184 kB)
  Cached:           1712 kB		(Active:           1200 kB)
  Cached:           1712 kB		(Active:           1180 kB)
  Cached:           1712 kB		(Active:           1180 kB)

  $ gzip -d < /boot/initrd_with_nuke | cpio -t >/dev/null 
  10227 blocks


=> Difference in memory (5304 kB) closely relates to initrd size.


Regards,
Peter