linux-kernel - Re: Hibernating To Swap Considered Harmful

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Message-Id: <200707141148.18279.rjw@sisk.pl>
Date:	Sat, 14 Jul 2007 11:48:17 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Joseph Fannin <jfannin@...il.com>
Cc:	david@...g.hm, "Huang, Ying" <ying.huang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	Jeremy Maitin-Shepard <jbms@....edu>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: Hibernating To Swap Considered Harmful

On Saturday, 14 July 2007 02:45, Joseph Fannin wrote:
> On Fri, Jul 13, 2007 at 11:30:50AM +0200, Rafael J. Wysocki wrote:
> > On Friday, 13 July 2007 07:42, Joseph Fannin wrote:
> > > On Thu, Jul 12, 2007 at 08:06:43PM -0700, david@...g.hm wrote:
> > > > On Thu, 12 Jul 2007, Rafael J. Wysocki wrote:
> > >
> > > > > Plus we need to figure out how to avoid corrupting filesystems and
> > > > > swap in use by the "old" kernel and its processes (hint: a separate
> > > > > "hibernation partition" is a no-go).
> > > >
> > > > I thought the existing hibernation wrote to the swap partition as it's
> > > > dedicated space?
> > > >
> > > > I didn't know that anyone was suggesting writing the hibernation image to
> > > > a filesystem that the kernel was activly accessing.
> > >
> > > I'm suggesting a dedicated, preallocated hibernation *file*, right
> > > now.  There's no way around it, if hibernation is to be reliable --
> > > otherwise hibernation can fail if the system has used enough of its
> > > swap space, so that there isn't enough room to write the hibernate
> > > image.
> > >
> > > Even if it's desirable to allow hibernation to fail if the system is
> > > too deep into swap, it's a moot point.
> >
> > If you're afraid of that, use a dedicated swap file.
> 
>     I don't understand what you mean.  A dedicated swap file for what?

Sorry, I should have been more precise.

For hibernation (ie. a swap file that you activate right befor the
hibernation).

Also tuxonice (formerly known as suspend2) allows you to use regular files
hibernation.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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