try setting the NKMEMPAGES kernel option.  it is limited to
1536 (6MB) which i found too few.  i've set mine to 4096 (16MB)
on a 128MB SS5 and it hasn't locked up or hung for a while.  it
lost for a number of reasons... but it wasn't until i finally
got the panic "out of space in kmem_map" that let me to increase
this value....


this (max) value has been bumped somewhat in -current...



.mrg.