ehrlich@psuvax1.bitnet (10/24/86)
From: ehrlich@psuvax1.bitnet
Is there a reason why temacs is not loaded with the "-n"
flag on BSD 4.2 systems? It would seem to be a reasonable thing
to do and the manual page does not indicate that "-n" is a
default option.
--Daniel Ehrlich
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===============================================================================guy@sun.uucp (Guy Harris) (10/24/86)
> Is there a reason why temacs is not loaded with the "-n" > flag on BSD 4.2 systems? It would seem to be a reasonable thing > to do Yes, there is a reason, namely that it is *not* a reasonable thing to do. Loading with the "-n" flag builds an executable image that must be loaded *all at once* when you "exec" it; both the Gosling/Unipress and GNU forms of EMACS are BMF programs, and you may not want to load lots of pages of code that you aren't going to use now or that you aren't going to use ever. > and the manual page does not indicate that "-n" is a default option. To be precise, the manual page indicates that "-z" is the default option, not "-n" (and definitely not "build an image with no shared text whatsoever", as you were probably assuming). "-z" "Arrange(s) for the process to be loaded on demand from the resulting executable file (413 format) rather than preloaded." This means that when the process takes a page fault, if the page has not already been loaded and placed on the swap device, it is loaded from the executable file. You don't read in any code unless you use it. -- Guy Harris {ihnp4, decvax, seismo, decwrl, ...}!sun!guy guy@sun.com (or guy@sun.arpa)
chris@umcp-cs.UUCP (Chris Torek) (10/29/86)
In article <3574@mit-eddie.MIT.EDU> ehrlich@psuvax1.bitnet writes: >Is there a reason why temacs is not loaded with the "-n" flag on >BSD 4.2 systems? It would seem to be a reasonable thing to do and >the manual page does not indicate that "-n" is a default option. Yes: it is not really all that reasonable. The 4.2 ld default is `-z': demand paged. `-n' makes the text shared, but not demand paged. Instead, on startup, the entire text is copied in to memory. If Emacs were to touch all its pages on startup, that would be sensible, but both Gnu and locally-hacked-Unipress touch only about half their pages. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu