[pups] bsd2.11 kernel compile

[Steven M. Schultz]

Hi!

> From: "Chuck Dickman" <chd_1 at nktelco.net>

	I see you beat me to the answer ;)

> During the compile 'size' outputs a list of the sizes of the
> overlays. Look at the output. For mine....
> 
> > How do I figure out which overlay (or base) is the problem?
> 
> The base must be less than 7 8k pages or 57344(decimal) bytes.
> Each overlay must be less than 8k bytes or 8192(decimal).
> The network code is not overlayed, so you have 8 pages or the
> full 64k. 

	And you use "size" on the .o files to see how much each object file
	contributes to an overlay.

	With the exception of a few .o files which *must* be in the base
	segment (and these are identified in the Makefile) anything can go
	anywhere it will fit.  The overlay switching is extremely efficient
	so don't worry about the 'affinity' of modules too much.

	Oh, it should be mentioned that it is not legal to have an empty 
	(0 length) overlay except at the end - i.e. you can't have overlay 3
	be 0 bytes if overlay 4 or higher has nonzero size.

> To make it work, just get the sizes below the limits. The 
> optimal arrangement would be placing the code in such that
> the overlay changes were minimized. So... move your system
> disk drivers into base and change the configuration to
> remove any hardware you don't actually have. 
	
	With the exception of perhaps the tty driver for the specific serial
	devices present on the system it's not worth trying to pack things
	"optimally".   The overhead of overlays is inhererent in the function
	prologue and epilogue - the only extra overhead of actually switching
	overlays is stuffing ~two words or so into the MMU registers.

	DO NOT remove anything from the actual OV lines in the makefile - just
	make sure you define/configure devices as not being present in the
	config file (by saying you have 0 of them).  Then the .o files do
	not take up any space and can be segregated into unused overlays
	at the end (OV9 or 10 or so).

	Good Luck!

	Steven Schultz
	sms at 2bsd.com