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Date: Wed, 29 Aug 2007 12:41:25 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: "Huang, Ying" <ying.huang@intel.com>
CC: "Hu, Fenghua" <fenghua.hu@intel.com>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Pavel Machek <pavel@ucw.cz>, nigel@nigel.suspend2.net,
       Andrew Morton <akpm@linux-foundation.org>,
       Jeremy Maitin-Shepard <jbms@cmu.edu>,
       Alan Stern <stern@rowland.harvard.edu>,
       linux-pm@lists.linux-foundation.org,
       Kexec Mailing List <kexec@lists.infradead.org>,
       linux-kernel@vger.kernel.org
Subject: Re: [linux-pm] [RFC][PATCH 0/2 -mm] kexec based hibernation
References: <9D7649D18729DE4BB2BD7B494F7FEDC257EA60@pdsmsx415.ccr.corp.intel.com> <1188180997.3247.68.camel@caritas-dev.intel.com>
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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.