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From: physh@unicom.UUCP (Jon 'Quality in - Quantity out' Foreman)
Newsgroups: comp.unix.wizards
Subject: Re: /dev/swap - possibility of it being a ramdisk
Message-ID: <213@unicom.UUCP>
Date: Tue, 8-Dec-87 00:46:32 EST
Article-I.D.: unicom.213
Posted: Tue Dec  8 00:46:32 1987
Date-Received: Sun, 13-Dec-87 10:30:57 EST
References: <712@qetzal.UUCP>
Reply-To: physh@unicom.UUCP (Jon 'Quality in - Quantity out' Foreman)
Organization: Halcon Co. et al., via College of Marin in California.
Lines: 42
Keywords: /dev/swap
Summary: Why make memory swap?

In article <712@qetzal.UUCP> rcw@qetzal.UUCP (Robert C. White) writes:
>Hello Wizards,
>
>Watching my poor little unix boxes swap, it occurred to me:
>why not utilize some extra ram to implement /dev/swap? It seems that
>the machine would speed up quite a bit, and hey, extra memory
>is pretty inexpensive, at least for the smaller 
>unix boxes. Also, it would be tactically easier to
>increase the amount of "swap" memory as opposed to repartitioning
>my disks, or mounting a disk pack under /tmp or some other 
>horrid kludge.
>
>I've never seen anyone mention this, and it may be that it would
>require major hacking on the kernel, but you guys know best...
>
>Robert White

	I would think that if you could put more memory in the machine,
you'd use it for main memory, which would also decrease swapping and
at the same time allow larger/more programs to run.  If memory got
big enough, you could do away with the swap space entirely (but
this will never happen, someone will always come up with a bigger
program.)

	I also question whether it is more effient to have the CPU
spend time copying blocks into and out of the swap space when a DMA
disk controller could do it with no CPU overhead, thus letting any
runable processes run.  Ram disks really only win big in single tasking
operating systems because you have to wait for the disk controller
anyway, and with a ram disk, you have to wait less time.  In
timesharing, you use the time swapping one person out to run someone
else.

	A friend of mine had an idea for a product which was a hugh
array of cheap slow memory which emulated a disk drive, and even would
have come in a disk drive case.  The object here was that there would
be no latency, and you could still hang it on a DMA disk controller.
Could this be what you're really looking for?
-- 
{ucbvax,hoptoad}!\                      ~~~~~~~\~~~   That's spelled
{lll-lcc,hplabs}!well!unicom!physh       Jon  }()      "physh" and 
         {ptsfa,dual}!/                        /     pronounced "fish".