[SOLVED] RE: [Backtrace] 4.9 and 5.1-RELEASE occasionly panic on RAM > 4GB without PAE (long)

First I would say "thank you" to those who helped me to find the cause of
the problem. Now I have confirmed that the problem goes away after a kernel
configuration tuning.

To trigger the problem, the box must have more than 2GB RAM and the
following configuration:

options         MAXDSIZ=(1024UL*1024*1024)
options         MAXSSIZ=(128UL*1024*1024)
options         DFLDSIZ=(1024UL*1024*1024)

A default, say, GENERIC kernel would not trigger panic's during my test.

The problem exists on 4-STABLE and 5-CURRENT, however, by increasing kernel
virtual address space by adding a line like the following:

options         KVA_PAGES=512

The panics goes away.

I would suggest the following patch against -HEAD to be applied:

Index: NOTES
===================================================================
RCS file: /home/ncvs/src/sys/conf/NOTES,v
retrieving revision 1.1192
diff -u -r1.1192 NOTES
--- NOTES       7 Dec 2003 04:41:11 -0000       1.1192
+++ NOTES       25 Dec 2003 06:36:27 -0000
_at__at_ -89,6 +89,12 _at__at_
 # and explicitly set the maximum with a shell command for processes
 # that regularly exceed the limit like INND.
 #
+# Adjusting these parameters may result in a larger kernel memory
+# usage. Thus you may want to enlarge kernel virtual address space.
+# On a i386 box with more than 2GB of memory and the following
+# options, KVA_PAGES=512 would be helpful to solve some fork related
+# kernel panics.
+#
 options        MAXDSIZ=(1024UL*1024*1024)
 options        MAXSSIZ=(128UL*1024*1024)
 options        DFLDSIZ=(1024UL*1024*1024)

Thank you again for your help!