How do I calculate UPAGES?

[speck at cit-vax.ARPA]

From:  Don Speck <speck at cit-vax.ARPA>

    Long ago, 4.2bsd on our vax was recompiled for 16 megabytes data
segment size.  It seems to have been accomplished by changing three
#define's:
		    old 	new	    file
	NDMAP	    16		36	/sys/h/dmap.h
	MAXDSIZ   12K-64      32K-64	/sys/vax/vmparam.h
	UPAGES	     8		10	/sys/vax/param.h

    MAXDSIZ is obvious (number of 512-byte pages), and NDMAP can be
figured out (4 entries for the 32K, 64K, 128K, 256K swap slots, plus
one entry for each 512K thereafter).  But the relationship between
UPAGES (pages of u-area?) and sizeof(struct user) is unclear.  Does
anyone know how this is supposed to be calculated?  What value of
UPAGES should I use when I raise NDMAP to 84 (40 Mb virtual memory)?

    Don Speck	speck at cit-vax.arpa  decvax!cithep!cit-vax!speck