Date: Mon, 8 Jul 1996 11:42:51 -0700 From: David McNab <mcnab@bayarea.net> To: robsch@robkaos.ruhr.de Cc: freebsd-fs@freebsd.org Subject: Re: procfs Message-ID: <199607081842.LAA27246@baygate.bayarea.net> In-Reply-To: <m0ud0Wu-0000IkC@robkaos.ruhr.de> (robsch@robkaos.ruhr.de)
next in thread | previous in thread | raw e-mail | index | archive | help
Robert wrote:
|Is it possible to freeze the current status of a process and
|restart it at a later time so that it begins execution at
|the point where it was frozen?
You can suspend it, which means it won't eat any
CPU time and can be easily paged out (won't consume any
memory -- well, hardly any). But this won't be
persistent across boots.
If you want real checkpointing -- the kernel
writes the executable and relevant context to a file
and can later restart it -- then the only UNIX OS I'm
familiar with that provides it, albeit in a slightly
limited way, is UNICOS, Cray's UNIX. The hardware
overhead's a bitch, though :^).
It's a hard problem. There's lots of state
scattered throughout the "system" that's hard to record
and regenerate. It's especially hard if you are doing
any networking, because then you have state in foreign
address spaces.
Most people seem to end up writing their number
cruncher so that it periodically hits a "sync point"
where they can easily checkpoint it themselves.
-- Dave McNab
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199607081842.LAA27246>