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Re: memory management issue (Re: another regression on Efika)

From: Robert Millan
Subject: Re: memory management issue (Re: another regression on Efika)
Date: Wed, 25 Jul 2007 22:08:05 +0200
User-agent: Mutt/1.5.13 (2006-08-11)

On Wed, Jul 25, 2007 at 12:51:27PM -0500, Hollis Blanchard wrote:
> I was indeed trying to make it absolute. GRUB is linked at 0x10000, or
> 64KB. Add in all the modules and you still are only using a couple
> hundred KB.

But if GRUB is linked at 0x10000, how come the firmware loads it since
that's below the 0x19111e4 limit?  (or am I missing some physical vs logical
issue here?)

> I don't remember *why* I was trying to make it absolute; I'm sure it
> was to fix a problem (rather than I was bored). If we could get away
> from this anachronistic Changelog crap, the commit message would have
> told us exactly what we need to know.

I pasted the ChangeLog entries in an earlier mail.  Do you mean the CVS commit
message might have more information?

> I *think* it was because we have a relocation problem with OSes that
> are linked at 4MB, which is the case with Xen (and I believe yaboot).
> If GRUB is using that memory, we simply can't load anything there.
> I think we can add some somewhat-special-case logic that says if there
> is nothing available below HEAP_LIMIT, claim something beginning as
> low as we can. That reduces functionality on such platforms (as
> described above), but there's little we can do about that unless
> firmware is fixed.

So the purpose of HEAP_LIMIT is to support code that is linked at fixed

> My big question is this: why is Efika firmware saying that 0x19111e4
> (around 25MB) is the first available address?

What is wrong with that?  Is it general practice that all firmwares load
at low addresses so that non-relocatable code can be linked at 4MB or such?

> BTW, does Jordi have any details on this Mac problem?

He said that after appliing the patch that makes heaplimit a relative address
it still won't work.  /memory/available:

  00003000 0000d000 0002d000 007d3000 00848000 1f3b8000

I'm CCing him.

Robert Millan

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