Re: Where is memory handed out?

From: Rick van Rein (vanrein@cs.utwente.nl)
Date: Mon Mar 20 2000 - 16:30:24 EST


Hi Nathan et al,

> [Where mem is handed out]
Thanx! I [already] got it working for i386!
Scary: Linux didn't crash a single time during this development...

I will submit a patch as soon as I resolved some remaining trouble with the
maximum length of cmdline arguments.

> Of course, this is a system-by-system hand-patched fix. We are working to
> permit a user to specify sections of memory to exclude. (ie: smap=20M-24M:X)

My scheme is somewhat closer to hardware I think:
        badram=adr0,mask0,adr1,mask1,...
where an address X is faulty if and only if (X & maskI) == (adrI & maskI)
for some I=0,1,...
This makes it simple (given experience with binary calculations) to capture
rows or columns from the RAM chips.

The scheme you propose (I am guessing what :X means) could be a problem for
further enhancements if it captures _more_ than the erroneous addresses.
An error-specification scheme that is close to hardware [like in my scheme
of address selection] makes it possible to narrow the discarded memory to
fit snugly around the error bits, for instance to provide slabs.

May I ask: What is the intention of this "smap" option; is it to use
damaged RAM or does it serve another purpose?

Cheers,
-Rick.

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