Kernel memory allocation oddities in NetBSD-10.99.12

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	hello.  I've been trying to track down a hard to reproduce lockup on one of my
NetBSD/amd64 10.99.12 machines.  As part of my investigation, I've realized the issue is most
likely related to some kernel memory allocation failure.  
This caused me to start monitoring the number of memory allocation failures, using the output
of vmstat -m, piped through an awk script  which calls out any allocations that have
experienced failures since the last reboot.

For example, on the machine, which has been up for 27 days, 22 hours, 
I see: 

biopl 272 3639296 2 3639204 54830 54584 246 532 0 inf 236
buf16k 16384 3380407 37 3355948 166739 157470 9269 13892 0 inf 0
pcgnormal 256 25244948 153624 25244528 496390 496356 34 1095 0 inf 7
pvpage 4096 1017753 8 1016052 474928 473227 1701 3701 0 inf 0
xnfrx 4096 1538484 20 1538196 127677 127386 291 435 0 inf 3
Totals 279028664 153691 275787771 3828646 3534742 293904


	The allocation category which fails the most is the pcgnormal, which is a fixed buffer of
256 bytes per allocation.  

	One question I have is, why would pcgnormal fail so often, while, at the same time, 

execargs    262144 2436031   0  2436030 30522 30509    13    16     0    16   12

which allocates far larger block sizes far more often, experience no allocation failures?  

If execargs can always find 200,000 bytes to allocate, how is it that pcgnormal or xnfrx, which
allocate 256 bytes and 4096 bytes respectively, cannot?

-thanks
-Brian