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

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Message-ID: <20110704100929.68674ea3@mschwide>
Date:	Mon, 4 Jul 2011 10:09:29 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-s390@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
	Len Brown <lenb@...nel.org>
Subject: Re: [patch 1/1] [PATCH] include storage keys in hibernation image.

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

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