Re: checkpointing page

[Eduardo Tongson <propolice () gmail com>]

> http://www.geocities.com/asimshankar/checkpointing/
fwiw
DragonFlyBSD <dragonflybsd.org> has checkpointing in its base with
similar caveats as the above implementation.

a snip from sys_checkpoint(2)
"""
CHECKPOINT FEATURES
     The system checkpointing code will save the process register state
     (including floating point registers), signal state, file descriptors rep-
     resenting regular files or directories (anything that can be converted
     into a file handle for storage), and both shared and private memory map-
     pings.  Private, writable mappings are copied to the checkpoint file
     while shared mappings and stored by referencing the file handle and off-
     set.  Note that the system checkpointing code does not retain references
     to deleted files, so mappings and open descriptors of deleted files can-
     not be restored.  Unpredictable operation will occur if a checkpoint-
     unaware program is restored and some of the underlying files mapped by
     the program have changed.

     The system checkpointing code is not able to retain the process pid,
     process group, user/group creds, or descriptors 0, 1, and 2.  These will
     be inherited from whomever restores the checkpoint.

     When a checkpointed program is restored modified private mappings will be
     mapped from the checkpoint file itself, but major portions of the origi-
     nal program binary will be mapped from the original program binary.  If
     the resumed program is checkpointed again the system will automatically
     copy any mappings from the original checkpoint file to the new one, since
     the original is likely being replaced.  The caller must not truncate the
     existing checkpoint file when creating a new one or specify the existing
     file's file descriptor as the new one as this will destroy the data that
     the checkpoint operation needs to copy to the new file.
"""

-- 
                                                    Eduardo Tongson
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