linux-kernel - Re: [linux-pm] [SUSPECTED SPAM] Re: Proposal for a new algorithm for reading & writing a hibernation image.

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Date:	Tue, 08 Jun 2010 12:07:13 +1000
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	TuxOnIce-devel <tuxonice-devel@...onice.net>
Subject: Re: [linux-pm] [SUSPECTED SPAM] Re: Proposal for a new algorithm
 for reading & writing a hibernation image.

Hi Rafael.

On 07/06/10 18:49, Rafael J. Wysocki wrote:
> On Monday 07 June 2010, Nigel Cunningham wrote:
>> On 07/06/10 05:04, Rafael J. Wysocki wrote:
>>> On Sunday 06 June 2010, Maxim Levitsky wrote:
>>>> On Sun, 2010-06-06 at 15:57 +0200, Rafael J. Wysocki wrote:
>>>>> On Sunday 06 June 2010, Maxim Levitsky wrote:
>>>>> So how TuxOnIce helps here?
>>>> Very simple.
>>>>
>>>> With swsusp, I can save 750MB (memory) + 250 Vram (vram)
>>>> With full memory save I can save (1750 MB of memory) + 250 MB of
>>>> vram....
>>>
>>> So what about being able to save 1600 MB total instead of the 2 GB
>>> (which is what we're talking about in case that's not clear)?  Would it
>>> be _that_ _much_ worse?
>>
>> That all depends on what is in the 400MB you discard.
>
> Well, they are discarded following the LRU algorithm and it's very much
> like loading a program that takes 20% of your memory upfront.
>
>> The difference is "Just as if you'd never hibernated" vs something
>> closer to "Just as if you'd only just started up". We can't make
>> categorical statements because it really does depend upon what you
>> discard and what you want to do post-resume - that is, how useful the
>> memory you discard would have been. That's always going to vary from
>> case to case.
>
> Not so much.
>
> Besides, it doesn't matter too much.
>
> Let me reiterate, please.  Doing serious memory management behind the back
> of the mm subsystem (and trying to do that so it doesn't notice) is wrong and
> the reason it works is by accident.  As long as you do that, I have a problem
> with TuxOnIce.

I know we're at a point where it doesn't matter what I say - you've made 
up you're mind and are not going to be persuaded by anything I say. 
We're degenerating from a technical discussion into emotive language.

This is why I object to the way you're picturing things. TuxOnIce isn't 
doing "serious memory management behind the back of the mm subsystem" or 
working "by accident". It's an algorithm that has been designed to rely 
on and use both the freezer and the existing mm subsystem to provide a 
means wherein we can get more reliable hibernation and a fuller image of 
memory.

May I suggest that we seek to get away from this point and focus on what 
we can agree on. Do you have any object to my work in the areas of:

- speed (async I/O, multithreaded I/O)
- flexibility (support for multiple swap devices, support for non swap, 
UUID support)
- tuneability (sysfs interface)
- anything else I might have forgotten to mention

If so, perhaps we can deal with those issues before I get too carried 
away preparing patches to get them merged.

Regards,

Nigel
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