linux-kernel - Re: [PATCH 0/3 -mm] kexec jump -v8

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Date:	Fri, 21 Dec 2007 16:53:27 +0800
From:	"Huang, Ying" <ying.huang@...el.com>
To:	nigel@...el.suspend2.net
Cc:	Kexec Mailing List <kexec@...ts.infradead.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH 0/3 -mm] kexec jump -v8

On Fri, 2007-12-21 at 19:35 +1100, Nigel Cunningham wrote:
> Hi.
> 
> Huang, Ying wrote:
> > This patchset provides an enhancement to kexec/kdump. It implements
> > the following features:
> > 
> > - Backup/restore memory used both by the original kernel and the
> >   kexeced kernel.
> 
> Why the kexeced kernel as well?

The memory range used by kexeced kernel is also the usable memory range
in original kernel. Maybe should be: backup/restore memory used by both
the original kernel and the kexeced kernel. My English is poor.

> [...]
> 
> > The features of this patchset can be used as follow:
> > 
> > - Kernel/system debug through making system snapshot. You can make
> >   system snapshot, jump back, do some thing and make another system
> >   snapshot.
> 
> Are you somehow recording all the filesystem changes after the first
> snapshot? If not, this is pointless (you'll end up with filesystem
> corruption).

This snapshot is not used for restore/resume. It is just used for
debugging. You can check the system state with these snapshots. So I
think it is useful even without recording filesystem changes.

> [...]
> 
> > - Cooperative multi-kernel/system. With kexec jump, you can switch
> >   between several kernels/systems quickly without boot process except
> >   the first time. This appears like swap a whole kernel/system out/in.
> 
> How is this useful to the end user?

I am not sure how useful is this. Maybe I can run a Redhat and a Debian
on my machine and switch between them.

Best Regards,
Huang Ying

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