18 Jun
2002
18 Jun
'02
5:11 a.m.
Hi!
From: "Chuck Dickman"
<chd_1(a)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....
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.
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. 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(a)2bsd.com