HEADS UP Re: cvs commit: src/sys/conf options.i386
src/sys/i386/i386 bios.c locore.s machdep.c mpboot.s pmap.c
vm86bios.s vm_machdep.c src/sys/i386/include _types.h bus_at386.h
jake at locore.ca
Sun Mar 30 12:04:56 PST 2003
Apparently, On Sun, Mar 30, 2003 at 01:31:18AM -0600,
Mike Silbersack said words to the effect of;
> On Sun, 30 Mar 2003, Jake Burkholder wrote:
> > To clarify that the ram above 4G is used for, it just goes into the general
> > page pool. I don't intend to implement a means for user process's to access
> > more then their ~2.5G address space through a sliding window as has been done
> > on other systems, but this should be quite easy to do should someone be so
> > inclined. To give an example, on a 6G system you see things like this:
> Cool, that's much better than the situation was for large ram machines
> before. :)
> Do these changes allow something like a 3G KVA space without shrinking
> processes address spaces?
No, it doesn't make the virtual address space any bigger, it just allows
more physical memory. This is a bit of a problem because the tunables that
are based on physical memory size don't scale well past 4G of ram, its easy
to end up with may too many vnodes.
> Also, I'm assuming that PAE can boot on machines with < 4 Gig of ram; can
Yes, you can use PAE on small memory machines. This will at least give you
compiler warnings about truncating physical addresses in most cases.
> it also be coaxed into acting in such a manner than busdma is _required_,
> so that a 256MB i386 box can be used to see if a driver is busdma
Not really. The best way is to buy a sparc :). I suppose that you could
create your dma tags such that busdma thinks it needs to bounce, this would
at least test that you've got the right bus_dmamap_syncs. ie set lowaddr to
below the highest physical address in your machine.
> In any case, very cool.
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