Re: [PATCH] Suspend2 Merge: Driver model patches 0/2

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > do it later:
> > > 
> > > Suspend all other drivers.
> > > Write pageset 2 (page cache).
> > > Suspend used drivers.
> > > Make atomic copy.
> > > Resume used drivers.
> > > Write pageset 1 (atomic copy)
> > > Suspend used drivers.
> > > Power down all.
> > 
> > What is problem with:
> > 
> > Write pageset 2
> > Suspend all drivers (avoiding slow operations)
> > Make atomic copy
> > Resume all drivers (avoiding slow operations)
> > Write pageset 1
> > Suspend all drivers
> > Power down all.
> 
> It's always interesting trying to remember your logic for doing
> something after the fact :>. If I recall correctly, it goes like this:
> 
> Writing two pagesets forces me to account for memory usage much more
> carefully. I need to ensure before I start to write the image that I
> know exactly what the size is and have allocated enough memory to do the
> write. If I get some driver coming along and grabbing memory for who
> knows what (hotplug, anyone? :>), I may get stuck halfway through
> writing the image with no memory to use. I also have to be paranoid
> about how much memory is available because I save that too (some of it
> may have become slab by the time I do the atomic copy).

What prevents video driver or disk driver to grab some memory? Tree
containing disk device can be pretty big [pci-usb-usb_hub-disk] and
contain some hot-pluggable components.

								Pavel
-- 
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