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gc-by-area and host uptimes

    Date: Thu, 9 Feb 89 11:55 EST
    From: David L. Andre <DLA@JASPER.SCRC.Symbolics.COM>

	Date: Thu, 9 Feb 89 11:19 EST
	From: Paul Pangaro <pan@Athena.Pangaro.Dialnet.Symbolics.Com>

	    Date: Thu, 9 Feb 89 09:38 EST
	    From: DLA@JASPER.SCRC.Symbolics.COM (David L. Andre)

		Date: Thu, 9 Feb 89 10:46:31 +0200
		From: luria%sel.technion.ac.il@RELAY.CS.NET (Marc Luria)


		what is this slow gc, and how slow is it?

	    SLOW-GC is a Symbolics-internal tool that was used in the development of
	    the Ivory GC and "operating system".  It is not a product, and it is
	    probably not what anyone suspects it is by looking at its name.

	Fine, but could you at least tell us what SLOW-GC 1does0 do? This leaves
	it hanging a bit, and treats us (though I dont think you intended it) as
	if as users our ignorance of things is OK, or we wouldnt understand if
	you told us what it does do.

    SLOW-GC was a mark-sweep GC which we wrote for early versions of Ivory
    whose GC and virtual-memory hardware was broken.  We had to write it to
    fit as much software as possible into the physical memory available (4MW).
    It is currently broken for Genera of all versions.  With the advent of
    :Start GC :Immediately By-Area, there's no pressing need for it either.

    By the way, it was actually pretty fast for the early Ivories, since there
    were no "real concerns" of working set, etc.  But it's attrociously slow
    on a full system, taking two to twelve hours (without-interrupts) for a
    typical dynamic GC.

    I was explicitly vague about all of this on the public list because I
    really didn't want to commit to shipping or supporting anything like this
    in the forseeable future.  There's an awful lot of work involved in making
    this into something that's near the quality of the system GC.

Thanks for the info. I dont think a mere mention of a hack implies the
future requirement for shipping or supporting; a disclaimer that it does
not work, is dangerous, etc., is not intended for users, should quiet
most folks from even asking for it. Then, your comment that :Start GC
:Immediately By-Area superceding its use or need can also be your final
comment on the matter. I was just lobbying for letting folks know
things, otherwise rumors get around and become stupid. You might end up
finding that you are being accused of hoarding an important tool that
solves all virtual memory problems ever considered, when in fact it
never even did what they thought it did...