Re: Back to the future.

From: Nigel Cunningham
Date: Thu Apr 26 2007 - 05:30:06 EST


On Thu, 2007-04-26 at 11:17 +0300, Pekka Enberg wrote:
> Hi Nigel,
> On 4/26/07, Nigel Cunningham <nigel@xxxxxxxxxxxxxxxxxx> wrote:
> > * Doing things in the right order? (Prepare the image, then do the
> > atomic copy, then save).
> As I am a total newbie to the power management code, I am unable to
> spot the conceptual difference in uswsusp suspend.c:suspend_system()
> and suspend2 kernel/power/suspend.c:suspend_main(). How are they
> different?

Will discuss in irc since you've appeared there...

> On 4/26/07, Nigel Cunningham <nigel@xxxxxxxxxxxxxxxxxx> wrote:
> > * Mulithreaded I/O (might as well use multiple cores to compress the
> > image, now that we're hotplugging later).
> I assume this doesn't affect the kernel at all with uswsusp?

Well uswsusp would benefit from using multiple threads - if it can - to
do the work. I saw quite an improvement from implementing it.

> On 4/26/07, Nigel Cunningham <nigel@xxxxxxxxxxxxxxxxxx> wrote:
> > * Modular design?
> This is too broad. Please be more specific of the problems the current
> suspend and snapshot/shutdown code in the kernel has.

Did you see the 'Reasons to merge' email I sent? It has more detail on

> Now to add to your list, as far as I can tell, suspend2 provides
> better feedback to the user via the netlink mechanism (although the
> kernel shouldn't be sending messages such as userui_redraw but instead
> let the userspace know of the actual events, for example, that tasks
> have now been frozen). However, I am unsure if this is still relevant
> as most of the work (snapshot writing) is being done in userspace
> where we explicitly know when processes have been frozen, when the
> snapshot is finished, and when it's written to disk.

From uswsusp's point of view, yeah. But I'm still coming from the 'doing
this in kernelspace makes far more sense' perspective.



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