linux-kernel - Re: Hibernation Redesign

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Message-Id: <200707120117.24549.a1426z@gawab.com>
Date:	Thu, 12 Jul 2007 01:17:24 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Mark Lord <lkml@....ca>, Jeremy Maitin-Shepard <jbms@....edu>
Cc:	Nigel Cunningham <nigel@...el.suspend2.net>,
	Miklos Szeredi <miklos@...redi.hu>, rjw@...k.pl,
	jeremy@...p.org, pavel@....cz, nickpiggin@...oo.com.au,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: Hibernation Redesign

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.  
And, it's not even necessary for a modular kernel, where you would only 
build in the drivers you need to hibernate.


Thanks!

--
Al

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