FreeBSD disk hibernation - Was: Resuming from a crashdump

• Previous message: takawata_at_jp.freebsd.org: "Re: Resuming from a crashdump"
• In reply to: Ryan Sommers: "Re: Resuming from a crashdump"
• Next in thread: Matthew Dillon: "Re: Resuming from a crashdump"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Date: Tue, 25 Jan 2005 00:21:05 -0200
To: hackers@freebsd.org

Ryan Sommers wrote:
> João Carlos Mendes Luís wrote:
>
>> Isn't it much easier to simply reload the full memory dump
>> (hibernation file, not dump device) into RAM and continue from that
>> point? This should be done by /boot/loader, not by a full kernel, as
>> the memory dump will also contain the kernel.
>>
>> At this point, all you have to do is to restore the hardware state,
>> which may (or may not) be just the same as recovering from suspend state.
>
>
> Restoring the hardware state requires restoring the state inside each
> and every hardware device. For certain devices this is trivial. However,
> I believe for devices with much more complex internal state machines
> this is way beyond the scope of the loader.

     This is not to be done by the loader. Loader will only load the
file into memory. It's this "running image" that will restore hardware
state.

> Now, that isn't to say the loader couldn't start executing the kernel
> somewhere other than "the beginning" and instead at a point where the
> kernel would specifically know it was awoken from hibernation and
> cleanup/reinitialize any devices.

     Almost this. Just note that we are not dealing with a kernel
anymore. If we have, someday, a swapable kernel, parts of it may be in
the swap, and not in core.

> My little knowledge on this subject aside. I'd love to have full
> suspend/resume functionality. It'd make my life as a mobile freebsd user
> much much easier. However, I wouldn't want it at the expense of every
> kernel. It would need to be something completely modular.

     It will require every driver used to be able to restore hardware
state, and this may impact every kernel a bit. Other than this, it
should be modular.

     BTW: This is not useful only for laptops. Some desktops could
benefit from this also. I like to hibernate windows XP desktops just to
continue processing from the same point on the next day, and do not
waste energy doing this. Maybe even some servers (mostly processing
servers, not network servers) could use this capability to survive
energy blackouts, hibernating when the UPS goes on battery for some time.

     I've thought on this before windows XP come with an implementation,
but I don't have enough knowledge to even start the hardware device
state setup. :-(

                                         Jonny

-- 
João Carlos Mendes Luís - Networking Engineer - jonny@jonny.eng.br
_______________________________________________
freebsd-hackers@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"

• Previous message: takawata_at_jp.freebsd.org: "Re: Resuming from a crashdump"
• In reply to: Ryan Sommers: "Re: Resuming from a crashdump"
• Next in thread: Matthew Dillon: "Re: Resuming from a crashdump"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]