Re: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation

david
2007-07-12T18:55:31Z

On Thu, 12 Jul 2007, Mark Lord wrote:

> Rafael J. Wysocki wrote:
>> On Thursday, 12 July 2007 08:43, david@lang.hm wrote:
>> > On Wed, 11 Jul 2007, Jeremy Fitzhardinge wrote:
>> >
>> > > Andrew Morton wrote:
> ..
>> > 8. hibernate kernel does syspend-to-ram to put the devices into a known
>> > safe state.
>> Again, the devices should be quiesced rather then suspended in this step.
>
> That's just not possible. The Hibernate kernel will not have all
> of the same device drivers as the mainline kernel. Or at least that's
> what people have previously stated here.

devices that have not been touches don't need to be quiesced or put into a
low-power state, they are still waiting to be initialized. so as long as
the device initialization can be done from the low-power or quiesced state
things will work just fine.

> ..
>> > > > This sounds awesome. Am I correct in expecting that ultimately the
>> > > > existing hibernation implementation just goes away and we reuse
>> > > > (and hence
>> > > > strengthen) the existing kexec (and kdump?) infrastructure?
>
> No, not so simple. We still need much of the code to santize devices
> upon wakeup from hibernation. And adding this extra reboot-kernel step
> in the midst of hibernate will double the time it takes (ugh).
>
> Currently, TuxOnIce(suspend2) takes about 10 seconds to suspend my notebook.
> Switching to this new scheme would double that to 10 seconds to boot/probe,
> plus the original 10 seconds to hibernate. Assuming the new implementation
> even comes close to suspend2 speed.

why do you assume that it will take 10 seconds to boot the new kernel?
linuxbiosdoes it in <2 seconds, someone else posted on this thread <5
seconds

> And the complexity and difficulty of setup really scares me.
> Right now, we've got a pretty good/fast in-kernel (well, external patch)
> that allows my machines to hibernate very quickly, wake up even faster,
> and not swap like mad afterwards. Without any external programs,
> initramfs, or extra kernels required.
>
> And we want to replace this with an ultra-complex setup because.. ????

the complexity of the freezer freezing some things, but not other things
keeps getting t wrong and many people can't think of any algorithm that
will always get it right. This approach bypasses the entire problem
makeing it much simpler conceptually, even though there are a few more
parts involved.

David Lang