Re: [PATCH 4/6] PM/Hibernate: Rework shrinking of memory

[Pavel Machek <pavel@ucw.cz>]

> > > > The main point (I thought) was to remove shrink_all_memory().  Instead,
> > > > we're retaining it and adding even more stuff?
> > > 
> > > The idea is that afterwards we can drop shrink_all_memory() once the
> > > performance problem has been resolved.  Also, we now allocate memory for the
> > > image using GFP_KERNEL instead of doing it with GFP_ATOMIC after freezing
> > > devices.  I'd think that's an improvement?
> > 
> > Dunno.  GFP_KERNEL might attempt to do writeback/swapout/etc, which
> > could be embarrassing if the devices are frozen.
> 
> They aren't, because the preallocation is done upfront, so once the OOM killer
> has been taken care of, it's totally safe. :-)

As is GFP_ATOMIC. Except that GFP_KERNEL will cause catastrophic
consequences when accounting goes wrong. (New kernel's idea of what is
on disk will differ from what is _really_ on disk.)

If accounting is right, GFP_ATOMIC and GFP_KERNEL is equivalent.

If accounting is wrong, GFP_ATOMIC will fail with NULL, while
GFP_KERNEL will do something bad.

I'd keep GFP_ATOMIC (or GFP_NOIO or similar). 

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html