Thus spake Terry Lambert <[EMAIL PROTECTED]>:
> I'm pretty sure Solaris also used 4K pages for swappable memory
> in the kernel, as well: 4M pages don't make much sense, since
> you could, for example, exhaust KVA space with 250 kernel modules
> (250 X (1 data + 1 code) * 4M = 2G).

It doesn't use 4M pages for all kernel memory---just the first 4M of
code and the first 4M of data.  Supposedly it also allows applications
to take advantage of 4M pages, though I'm not sure how that works.  At
the very least I'd suppose that those pages are locked into memory.

> I don't know where the Linux limitation comes from; it's really
> hard for me to believe "~3G", since it's not an even power of 2,
> so I don't really credit this limitation.

I don't really understand it either.  I could try to find the link to
where I found this information if you're interested, but I wouldn't be
surprised if it is simply wrong.  The 2.4 kernel docs seem to imply
that 2.4 can use 4 GB of RAM without PAE.

> No problem; I think you will have to, if you are planning on
> mucking about with more than 4G of physical memory.

I have no such plans in the immediate future; at this point the
discussion is a curiosity.  But with any luck I will already know
what's going on by the time I need to worry about tweaking the kernel
in bizarre ways.

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