linux-kernel - Re: Hibernation considerations

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Message-ID: <469A3EB9.8000304@gmail.com>
Date:	Sun, 15 Jul 2007 21:05:21 +0530
From:	jimmy bahuleyan <knight.camelot@...il.com>
To:	Al Boldi <a1426z@...ab.com>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.linux-foundation.org>, david@...g.hm
Subject: Re: Hibernation considerations

Al Boldi wrote:
> 
> This should be the responsibility of the kexec'd hibernating kernel.  Note 
> though in (6), the normal kernel takes care of preparing devices, then the 
> hibernating kernel dumps the image and either calls S4 or S3.  On resume 
> from S3 it can immediately switch over to the normal kernel, and from S4 the 
> known bootup would occur.
> 
>> (8) Hibernation and restore should not be too slow
>>
>>     In my opinion, if more than one minute is needed to hibernate the
>> system with the help of certain hibernation framework, then this framework
>> is not very useful in practice.  It might be useful to perform some
>> special tasks (eg. moving a server to another place without taking it
>> down), but it is not very useful, for example, to notebook users.
> 
> The latest hibernating kexec patches boot a kexec'd modular kernel with 
> initramfs into crashkernel=16M@16M in less than one second.  Switch-back is 
> almost instant.  Add to this the time required to either store or restore 
> the image, and it may be obvious that this approach isn't slower, but maybe 
> even faster than the current swsusp.
> 

What about (9)? Would it be that a user choosing to build a kernel with
hibernate support gets a additional modular kernel built (which he
should then use for resumption) or he should configure & build the
modular kernel independent of main kernel?

Or will the Linux boot procedure change so that it always goes thru a
modular part followed by kexec (just to be uniform)?

Although the kexec approach seems interesting, the final user-scenario
seems a bit complex (or confusing).

-jb
-- 
Tact is the art of making a point without making an enemy.
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