DragonFly BSD
DragonFly kernel List (threaded) for 2003-09
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Re: checkpoint/restart milestone 1

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 15 Sep 2003 01:10:09 -0700 (PDT)

:	Ah, sounds good!  I looked into this idea some time ago, when
:	you can suspend a process, store it's state in an image file
:	and then you can use it whenever you want for reloading it
:	back.
:	The only issue I had with such kind of thing was to do with the
:	state that the kernel keeps, like file descriptor tables, and
:	vnode references, which are invalidated after a reboot, because
:	a new table is created.
:	One way to solve this problem was to index into the filedesc
:	table and make out which files were open, save this information
:	in some sort part of the process image, and then when the
:	image is loaded, we recreate references to the files originally
:	referenced; although, this is just an overall perspective on the
:	topic.  I am sure there were other roadblocks which I faced.
:	Anyway, this sounds ilke a really good idea!  :-)
:	Regards,
:Hiten Pandya

    Yah.  Obviously the feature will start out being rather primitive, but
    it should be possible to add functionality incrementally without having
    to ripup the stuff already done.  I can envision (in the future) a 
    program setting up a SIGCHKPT signal, for example, which would allow the
    program to implement its own checkpoint restore function based on a
    resource list given to it by the system.

					Matthew Dillon 

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