Re: x86_64 ten times slower than i386

[Willy Tarreau]

On Mon, Nov 05, 2007 at 05:19:44PM -0800, H. Peter Anvin wrote:
> Andi Kleen wrote:
> >>Jesse Barnes (cc:d) wrote a patch to address this, I think (x86: trim
> >>memory not covered by WB MTRRs), but as far as I can tell it hasn't
> >>been merged yet. System is Intel, 4gb of RAM.
> >
> >It wasn't merged because it broke booting on some systems.
> >Besides the memory would be still lost -- all it did was to automate
> >the "mem=XXXX" line.
> 
> There really are only two ways to deal with this -- drop the memory 
> (which should be automated, and a warning printed) or adjust the MTRRs. 
>  The problem is that at some point we run out of MTRRs, partially 
> because they're masks instead of base/limit.

Just out of curiosity, what would be the problem if the MTRRs covered more
than the memory size ? For instance, instead of having 512 MB at 4G, why
not have 1G at 4G ?

regards,
Willy

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/