Messages in this thread | | | Subject | Re: [RFC v6][PATCH 0/9] Kernel based checkpoint/restart | From | Dave Hansen <> | Date | Thu, 09 Oct 2008 06:34:06 -0700 |
| |
On Thu, 2008-10-09 at 15:17 +0200, Ingo Molnar wrote: > * Dave Hansen <dave@linux.vnet.ibm.com> wrote > > On Thu, 2008-10-09 at 14:46 +0200, Ingo Molnar wrote: > > > i'm wondering about the following productization aspect: it would be > > > very useful to applications and users if they knew whether it is safe to > > > checkpoint a given app. I.e. whether that app has any state that cannot > > > be stored/restored yet. > > > > Absolutely! > > > > My first inclination was to do this at checkpoint time: detect and > > tell users why an app or container can't actually be checkpointed. > > But, if I get you right, you're talking about something that happens > > more during the runtime of the app than during the checkpoint. This > > sounds like a wonderful approach to me, and much better than what I > > was thinking of. > > > > What kind of mechanism do you have in mind? > > > > int sys_remap_file_pages(...) > > { > > ... > > oh_crap_we_dont_support_this_yet(current); > > } > > > > Then the oh_crap..() function sets a task flag or something? > > yeah, something like that. A key aspect of it is that is has to be very > low-key on the source code level - we dont want to sprinkle the kernel > with anything ugly. Perhaps something pretty explicit: > > current->flags |= PF_NOCR;
Am I miscounting, or are we out of these suckers on 32-bit platforms?
> as we do the same thing today for certain facilities: > > current->flags |= PF_NOFREEZE; > > you probably want to hide it behind: > > set_current_nocr();
Yeah, that all looks reasonable. Letting this be a dynamic thing where you can move back and forth between the two states would make a lot of sense too. But, for now, I guess it can be a one-way trip.
I'll cook something up real fast.
-- Dave
| |