Re: Suggestion for laptop suspension

From: Pavel Machek (
Date: Mon Aug 28 2000 - 17:16:22 EST


> > 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.

I'm "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at
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