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SubjectRe: Suggestion for laptop suspension
Hi!

> > is how to mark memory as "unused". I had a theory that the APM BIOS
> > suspend code was checking if the memory was all zero's, and not writing
> > such pages to disk. This was a while ago, but a quick test didn't seem
> > to bear out this theory.
>
> Are you sure? Maybe the block of zero memory must be continuous at the
> end, in which case fragmentation would certainly spoil this.
>
> No, I'm not sure. As I said, I did a quick test, and when the obvious
> thing didn't bear fruit, I lost interest and dropped it. It could have
> been that I screwed up the test somehow. It also could have been that
> the BIOS was using some other flag value (0xFF, etc.). There's a lot of
> really easy tests that could have been done, that I didn't have time to
> do.
>
> There still is the question of whether anything we do to speed this up
> would be laptop specific or not. I'm not an APM BIOS expert, so someone
> like Stephen Rothwell would be much better equipped to comment on this
> issue.

You *dont* need bios support to do suspend-to-disk, as swsusp
shows. That is generic across all machines. I believe improving swsusp
(it is pretty slow these days, partly because it trashes all caches:
it does so by applying artifical memory pressure) is much better
project than trying to find out what value do you need in order for
BIOS to compress ram.
Pavel
--
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
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