Re: [linux-pm] [RFC][PATCH 0/2 -mm] kexec based hibernation

[Nick Piggin <nickpiggin@yahoo.com.au>]

Huang, Ying wrote:
> On Mon, 2007-08-27 at 09:28 +0800, Hu, Fenghua wrote:
> 
>>One quick question is, can it improve hiberation/wakeup time?
> 
> 
> In general, for kexec based hibernation, what increases
> hibernation/wakeup time:
> 
> - One extra Linux boot is needed to hibernate and wakeup.
> 
> 
> What decreases hibernation/wakeup time:
> 
> - Most hibernation/wakeup work is done in full functional user space
> program, so it is possible to do some optimization, such as parallel
> compression.

- It does not have to reclaim pagecache before suspend?

- It does not have to restore working set afterwards?

(You could do this to reduce image size, of course, but it can
be optional which is nice).


> So, I think the kexec based hibernation may be slower than original
> implementation in general. In this prototype implementation, the
> hibernation/wakeup time is much longer than original hibernation/wakeup
> implementation. But it has much to be optimized and I think it can
> approach the speed of the original implementation after optimization.

Also, don't just look at the time to do a simple suspend/resume cycle,
but the full cost of going from working state to working state (eg.
grep a kernel tree or two!).

Although the kexec details are out of my league, I really like
everything about the concept :) Nice work.

-- 
SUSE Labs, Novell Inc.