Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sco!seanf
From: seanf@sco.COM (Sean Fagan)
Newsgroups: comp.unix.sysv386
Subject: Re: Take out memory to speed up kernel build!?
Message-ID: <7986@scolex.sco.COM>
Date: 2 Oct 90 23:59:00 GMT
References: <34417@cup.portal.com> <4133@altos86.Altos.COM>
Sender: news@sco.COM
Reply-To: seanf (Sean Fagan)
Organization: The Santa Cruz Operation, Inc.
Lines: 28


In article <4133@altos86.Altos.COM> steve@Altos.COM (Steve Scherf) writes:
>In article <34417@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes:
>>I've got 4 megs of RAM, and the command /etc/conf/cf.d/link_unix
>>takes about 7.5 minutes.
>>When my back was turned the other day, one of our QC people
>>stole my memory card, leaving me with only 2 meg.
>>Guess what?  My kernel build now takes only 5 minutes!
>
>Can you be more specific about the environment under which you tried this?

If Tim has a 386DX processor, and the memory card was a 16-bit card, then I
am not surprised.  What ends up happening, in a lot of cases, is that the
kernel snarfs up all of the 32-bit "fast" memory, and puts user code into
the 16-bit "slow" memory ("fast" and "slow" because of number of cycles
needed to get a full word).  It does this because, as far as it knows, there
is no difference; all it sees is one large chunk of memory.

With the 16-bit memory gone, then, of course, the kernel has to make do with
the lesser amount of memory.  Depending on the size of the kernel, the
number of various buffer, activity, etc., 2Mb can end up faster than 4Mb.

-- 
-----------------+
Sean Eric Fagan  | "Never knock on Death's door:  ring the bell and 
seanf@sco.COM    |   run away!  Death really hates that!"
uunet!sco!seanf  |     -- Dr. Mike Stratford (Matt Frewer, "Doctor, Doctor")
(408) 458-1422   | Any opinions expressed are my own, not my employers'.