Subject: Re: 7GB memtest causes hard system hang.
To: Frank van der Linden <email@example.com>
From: Greg Oster <firstname.lastname@example.org>
Date: 01/16/2006 15:47:30
Frank van der Linden writes:
> On Mon, Jan 16, 2006 at 11:33:08AM -0600, Greg Oster wrote:
> > (Without the "options NKMEMPAGES=150000" tweak, the machine is basically
> > useless to me -- I can easily run "too much stuff" that gets me to the
> > "no pv entries available" panic :( )
> > The proper fix is to fix the pmap code. A short-term workaround is to
> > do the NKMEMPAGES bump above...
> The pmap code isn't really the problem here. Running out of kernel
> memory (kmem_map in this case) is hard to recover from. With the current
> setup, all that we can do is set nkmempages to a better default value.
> Currently, the default maximum for amd64 is still 128M, which is way
> too low for machines with > 4G of memory. 1G is probably a better
> value for those. Tuning these parameters is somewhat of a black art.
I forget what the "critical point" was, but I just found it very
annoying that a machine w/ 4GB RAM *free* couldn't automatically find
a bit more for the kernel to use... (There's gotta be a way to
reserve some pages for these sorts of "emergencies" so that
"something" can grab more memory for the kernel..) kmem_map should
automatically expand/shrink as demand warrants... I'm not sure I
want to learn that much about that part of the kernel to attempt to
fix that though :)