linux-kernel - Re: Hibernation Redesign

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Message-Id: <200707120034.14201.rjw@sisk.pl>
Date:	Thu, 12 Jul 2007 00:34:12 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Al Boldi <a1426z@...ab.com>
Cc:	Mark Lord <lkml@....ca>, Jeremy Maitin-Shepard <jbms@....edu>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Miklos Szeredi <miklos@...redi.hu>, jeremy@...p.org,
	pavel@....cz, nickpiggin@...oo.com.au,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: Hibernation Redesign

On Thursday, 12 July 2007 00:17, Al Boldi wrote:
> Mark Lord wrote:
> > Jeremy Maitin-Shepard wrote:
> > > I'll certainly admit the kexec idea is vaporware currently,
> 
> Your idea is starting to become a reality with this thread:
> "[PATCH 0/2] Kexec jump: The first step to kexec base hibernation"
> 
> > > but it does
> > > differ in a significant way from freezer-based approaches, such that I
> > > don't think it should be referred to as just another implementation of a
> > > freezer.  Specifically, it doesn't require that the "old kernel" be in a
> > > "consistent" state to a greater extent than suspend to ram; it is the
> > > case that all of the devices must be quiesced or shut down to some
> > > extent, but doing this without races and deadlocks (and without the
> > > freezer) is certainly very, very similar to what needs to be done for
> > > suspend to ram, which will need to be solved anyway.  Unlike the
> > > existing hibernate approaches, however, it will not be necessary to use
> > > any of the driver infrastructure once switched to the "save image"
> > > kernel, and thus it will not matter what locks are held, for instance.
> >
> > I really doubt that kexec(a special kernel) is going to solve anything
> > here. The new kernel will have to initialize, probe for devices, etc.
> > Which will take time.
> > Which will slow down hibernate to an unacceptable degree.
> > Right now, it (TuxOnIce) is *very* fast.
> > Adding 10 seconds or so for reprobing/resetting/reiniting devices
> > is not going to be useful.
> > And modifying all of the drivers to *not* do their usual probe sequence
> > sounds rather intrusive and is likely also a non-starter here.
> >
> > Or is it?
> 
> Well, it's definitely less intrusive than readying drivers for the freezer.

There's nothing like this!

Greetings,
Rafael


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