1998Q2/
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<H1>Re: [MUD-Dev] Re: MUD Development Digest</H1>
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<LI><em>To</em>: <A HREF="mailto:mud-dev#null,net">mud-dev#null,net</A></LI>
<LI><em>Subject</em>: Re: [MUD-Dev] Re: MUD Development Digest </LI>
<LI><em>From</em>: "Jon A. Lambert" &lt;<A HREF="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</A>&gt;</LI>
<LI><em>Date</em>: Thu, 9 Apr 1998 01:51:35 -5</LI>
<LI><em>Reply-to</em>: <A HREF="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</A></LI>
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<PRE>
On  8 Apr 98 at 13:33, J C Lawrence wrote:
&gt; On Sat, 4 Apr 1998 09:39:55 PST8PDT 
&gt; Justin McKinnerney&lt;xymox#toon,org&gt; wrote:
&gt; 
&gt; &gt; First, I agree with your first comment. I have heard people claim
&gt; &gt; their disk-based muds run faster than memory-based, but this all
&gt; &gt; semantics. If a disk-based game does run notably faster than it's
&gt; &gt; memory-based equivilant, it's simply due to the fact the operating
&gt; &gt; system is doing a better job of memory managment (perhaps doing
&gt; &gt; cache alignment, for instance), which wouldn't be suprising
&gt; &gt; considering some of the code for MUDs I have seen.
&gt; 
&gt; No.  Typically it has nothing to do with the OS'es memory supports,
&gt; but has to do with working __around__ the OS'es memory model as it
&gt; is inefficient for the task at hand.  The performance gains are due
&gt; to the fact that the disk-based game uses intelligent cacheing which
&gt; forces a (reasonably) minimum number of pages for the game's working
&gt; set.  Its not very difficult to put the entire world in RAM, and
&gt; then chew all your performance with page faults -- or to get it back
&gt; again by keeping some of the disk IO, but losing the constant page
&gt; faults.

Speaking of page faults... there are issues of implementation which,
if transgressed often enough, make for some bottlenecks in this area
outside of the disk vs. memory issue.

For example:

 This will cause 5000 page faults...

 for (col = 0; col &lt; 1000; col++)
  for (row = 0; row &lt; 5; row++)
           table[row , col] = 0;

 And this about 5 page faults

 for (row = 0; row &lt; 5; col++)
      for (row = 0; col &lt; 1000; row++)
           table[row , col] = 0;


The same scenario also occurs in good size link lists, where the
objects have been allocated haphazardly by a fiendish malloc().

There are many possible solutions.  I grab a hefty chunk of memory,
mark it unswappable and stay within that playground.  Then page out
unreferenced or least-referenced objects to disk as needed. You CAN do
a much better job at application memory management than the operating
system can.   

 
--
--/*\ Jon A. Lambert - TychoMUD     Internet:jlsysinc#ix,netcom.com /*\--
--/*\ Mud Server Developer's Page &lt;<A  HREF="http://www.netcom.com/~jlsysinc">http://www.netcom.com/~jlsysinc</A>&gt; /*\--
--/*\   "Everything that deceives may be said to enchant" - Plato   /*\--

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<UL><LI><STRONG>References</STRONG>:
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<LI><STRONG><A NAME="00016" HREF="msg00016.html">RE: [MUD-Dev]  Re: MUD Development Digest</A></STRONG>
<UL><LI><EM>From:</EM> "Justin McKinnerney" &lt;xymox#toon,org&gt;</LI></UL></LI>
<LI><STRONG><A NAME="00075" HREF="msg00075.html">Re: [MUD-Dev] Re: MUD Development Digest</A></STRONG>
<UL><LI><EM>From:</EM> J C Lawrence &lt;claw#under,engr.sgi.com&gt;</LI></UL></LI>
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<ul><li>Thread context:
<BLOCKQUOTE><UL>
<LI><STRONG>Re: [MUD-Dev] Re: MUD Development Digest</STRONG>, <EM>(continued)</EM>
<ul compact>
<ul compact>
<ul compact>
<ul compact>
<LI><strong><A NAME="00082" HREF="msg00082.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Thu 09 Apr 1998, 02:22 GMT
</LI>
</ul>
<LI><strong><A NAME="00081" HREF="msg00081.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Thu 09 Apr 1998, 01:48 GMT
<UL>
<LI><strong><A NAME="00088" HREF="msg00088.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
Alex Oren <a href="mailto:alexo#bigfoot,com">alexo#bigfoot,com</a>, Thu 09 Apr 1998, 11:31 GMT
</LI>
</UL>
</LI>
</ul>
<LI><strong><A NAME="00075" HREF="msg00075.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 08 Apr 1998, 20:23 GMT
<UL>
<LI><strong><A NAME="00086" HREF="msg00086.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
Jon A. Lambert <a href="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</a>, Thu 09 Apr 1998, 05:48 GMT
</LI>
</UL>
</LI>
</ul>
<LI><strong><A NAME="00073" HREF="msg00073.html">Re: [MUD-Dev] Re: MUD Development Digest</A></strong>, 
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 08 Apr 1998, 18:22 GMT
</LI>
<LI><strong><A NAME="00762" HREF="msg00762.html">[MUD-Dev] Re: MUD Development Digest</A></strong>, 
J C Lawrence <a href="mailto:claw#under,engr.sgi.com">claw#under,engr.sgi.com</a>, Wed 22 Apr 1998, 18:40 GMT
<UL>
<LI><strong><A NAME="00346" HREF="msg00346.html">[MUD-Dev] Re: MUD Development Digest</A></strong>, 
Ben Greear <a href="mailto:greear#cyberhighway,net">greear#cyberhighway,net</a>, Thu 23 Apr 1998, 02:56 GMT
<UL>
<LI><strong><A NAME="00360" HREF="msg00360.html">[MUD-Dev] Re: MUD Development Digest</A></strong>, 
Jon A. Lambert <a href="mailto:jlsysinc#ix,netcom.com">jlsysinc#ix,netcom.com</a>, Thu 23 Apr 1998, 05:58 GMT
</LI>
</UL>
</LI>
</UL>
</LI>
</ul>
</LI>
</UL></BLOCKQUOTE>

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