Subject: Re: 7GB memtest causes hard system hang.
To: Frank van der Linden <>
From: Chuck Silvers <>
List: port-amd64
Date: 01/18/2006 09:07:30
On Mon, Jan 16, 2006 at 10:22:24PM +0100, Frank van der Linden wrote:
> 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.

this is also the cause of PR 32157, kmem_map fills up and then we go into
an infinite loop trying to allocate more memory.

is there any reason we shouldn't increase NKMEMPAGES_MAX_DEFAULT to 1 GB
at this point?