sticky bit

[was-John McMillan]

In article <25591 at wlbr.EATON.COM> jm at wlbr.eaton.com (James Macropol) writes:
...
>I once modified a V7 PDP-11 UNIX system to save a prototype of the  data
>out on the swap  file, too.   It took about twenty  lines of changes  in
>text.c, text.h and exec.c (I think.  My memory is getting hazy).
>
>Unlike the standard  sticky texts,  this DID  help shared-text  programs
>that already had another incarnation running, because it DRASTICALLY cut
>down on the number of reads necessary to initialize the data segment (to
>one).  On some large programs, it  cut down program load time by  almost
>two seconds.

Yup -- 'did it three years ago on the 3B1/7300 and it was a FLASH start-up...
but o' that swap space!  Fortunately, the faster and faster disks
have made these tricks rather unnecessary when combined with Paging.

PS:
1) I agree with much of what DLM said: the SB does introduce DIS-MOUNT
	anomalies.  One strategy is to only Stick it to ROOTDEV programs.
   The gain it provides on paging systems can, indeed, be very small --
	particularly, when the disk was well-ordered at the time
	the programs were loaded, when the disk-access rates are
	fast, when shared libraries are used, and particularly,
	I would presume, if sequentially allocated disk sectors were
	allocated to executable files -- a trick I've heard of, but
	never seen.
   However, on the 3B1/7300, even with its paging, the times are quite
	measurable, Dennis!

2) In article <314 at twwells.uucp> Bill writes:
...
	>Depends on the system. Mine will move stuff out of swap if it's not
	>in use and the space is needed. Read the chmod(2) manual page to see
	>what yours does.

	Nice! How common is this?  What is your system?  Now
	I've got to scurry through SVR3.2 sources, I suppose ;-{
	'Don't recall the 3B1 being that considerate, however.

	>I just did my editor, compiler, make, and ls.

	All nice packages to be sure:  But with shared libraries,
	LS is only 2 to 4 [4K] pages of TEXT.  All EDITORS are great
	targets: you're poised over the keyboard and their TEXT
	runs towards 30 pages.  Shells run 10 to 20 pages, so they're
	a WIN.  Compiler & Make?  Lucky you, getting to write software! %-}

jc mcmillan	-- att!mtunb!jcm	-- juzz muttering for hizzelf