Date: Mon, 21 Feb 94 22:16:32 PST
From: stevev AT miser DOT uoregon DOT edu (Steve VanDevender)
To: Raymond Rosmalen <raymond AT hef DOT kun DOT nl>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: RAM drive

Raymond Rosmalen writes: 

 > Hi, I've been trying to improve on compilation time by making
 > a RAM drive.  I have in total 3MB XMS memory from which 1MB is
 > in use by SMARTDRV. I made an 1MB RAM drive in XMS memory.
 > Next, the TMPDIR varaiable was set to point to the RAM drive.
 > 
 > Now I compiled a small (about 50 lines) program and this took
 > me about 15 minutes (1MB RAM drive, 1MB XMS) !!  Without the
 > RAM drive it `only' took me 1.5 minutes (0MB RAM drive 2MB
 > XMS).
 > 
 > My question is: Did I forget something in setting up a RAM
 > drive or is 3MB XMS memory just not enough?  Or maybe, should
 > I have created a smaller (or larger) RAM drive instead?  Any
 > comments are more than welcome!

Welcome to the wonderful world of virtual memory.  You are
probably better off running GCC without either a ramdisk _or_ a
disk cache, since GCC needs at least 2M by itself, and having
less than 2M of free physical memory will result in it paging to
disk.  A ramdisk and a disk cache together will reduce
performance, as you saw, since your system will spend a lot of
time moving stuff between them, taking CPU time away from your
compilation.  A small disk cache (perhaps 256K or 512K) alone
_might_ help, by reducing somewhat the amount of access neded to
the physical disk.