Re: [patch 1/1] [PATCH] include storage keys in hibernation image.

[Martin Schwidefsky <schwidefsky@de.ibm.com>]

On Sun, 3 Jul 2011 19:46:16 +0200
Pavel Machek <pavel@ucw.cz> wrote:

> Hi!
> 
> > > I think, however, that we really should try to merge them.  The only
> > > difference seems to be how the additionally allocated pages will be populated
> > > and what's going to happen to their contents during restore.
> > > 
> > > ACPI will simply copy the NVS memory to those pages, while S390 will save
> > > the relevant storage key bits in there.
> > 
> > One complication to keep in mind is that we need to know which storage key
> > goes to which page frame. We need something like the orig_bm/copy_bm or
> > we'd have to store the pfn with the key. Simply storing the key for every
> > page will make the array unnecessarily big.
> 
> How big is the overhead? In percent / in megabytes?

Well, that depends on the ratio of the size of the hibernation image and
the total size of the ram. Consider a 1TB machine with a hibernation image
size of lets say 128 GB. The hibernation image would require 32 MB worth
of storage keys (0.024%), for 1TB the array size would be 256 MB (0.19%).

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.