Re: [ 01/10] [Suspend2] kernel/power/modules.h

[Nigel Cunningham <nigel@suspend2.net>]

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Hi.

On Friday 03 February 2006 23:16, Pavel Machek wrote:
> On Pá 03-02-06 10:20:42, Nigel Cunningham wrote:
> > Hi.
> >
> > On Friday 03 February 2006 08:10, Rafael J. Wysocki wrote:
> > > On machines with less RAM suspend2 will probably be better
> > > preformance-wise, and that may be more important than the flexibility.
> >
> > Ok. So I bit the bullet and downloaded -mm4 to take a look at this
> > interface you're making, and I have a few questions:
>
> Great, thanks.
>
> > - It seems to be hardwired to use swap, but you talk about writing to a
> > network image above. In Suspend2, I just bmap whatever the storage is,
> > and then submit bios to read and write the data. Is anything like that
> > possible with this interface? (Could it be extended if not?)
>
> No, it is not hardwired. There's special swap support, but you do not
> need to use it.
>
> > - Is there any way you could support doing a full image of memory with
> > this approach? Would you take patches?
>
> Doing full image is certainly possible; it is not important if kernel
> does the writing or userspace does it. Taking patches definitely
> depends how they'd look like...

Would you actually do some work on generating them? I'm concerned that I'm 
going to end up putting more work into making patches, only to have you nack 
them for (what seem to me like) arbitrary reasons. I feel like all you're 
doing at the moment is pouring cold water on my work. Seeing you put some 
work into making mileage from the work I've put into Suspend2 would encourage 
me a lot. Forgive me if I sound pretty negative - between a couple of months 
of humid weather, lack of sleep and the event of the last few weeks, I'm not 
in the best frame of mind at the moment. Perhaps it would be better for me 
just to say "I give full permission for you and Rafael to rip out of Suspend2 
anything you find useful.", leave it at that and go find another hobby for a 
while.

Regards,

Nigel

> > - Does the data have to be transferred to userspace? Security and
> > efficiency wise, it would seem to make a lot more sense just to be
> > telling the kernel where to write things and let it do bio calls like I'm
> > doing at the moment.
>
> As far as I can see, transfering data to userspace and back does not
> really cost much:
>
> pavel@amd:~$ time head -c $[1024*1024*1024] < /dev/zero > /dev/null
> 0.16user 0.27system 0.43 (0m0.439s) elapsed 100.00%CPU
>
> ...2000MB/sec is the limit (thinkpad x32).
> 								Pavel

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