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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>But we execute the same binary in the same
path for each server…? Why the <span class=SpellE>symlink</span>?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>------------------------------------<o:p></o:p></span></font></p>
<div>
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style='font-size:12.0pt;color:navy;mso-no-proof:yes'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy;mso-no-proof:yes'> </span></font><o:p></o:p></p>
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<p class=MsoNormal style='margin-left:36.0pt'><font size=2 face=Tahoma><span
lang=EN-US style='font-size:10.0pt;font-family:Tahoma;mso-ansi-language:EN-US'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> Mark J. DeFilippis
[mailto:defilm@acm.org<span class=GramE>] <br>
<b><span style='font-weight:bold'>Sent</span></b></span><b><span
style='font-weight:bold'>:</span></b> 25 September 2004 20:33<br>
<b><span style='font-weight:bold'>To:</span></b> cod@icculus.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [cod] Semi off topic:
COD rentals</span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
You are thinking application level. This is Kernel level.<br>
I spent lots of time in my career developing real time embedded coding<br>
in Unix/Linux kernels.<br>
<br>
Look at two linuxded files that are not sym linked. But use this:<br>
<br>
ls -li<br>
<br>
Note the left side has a value called an inode. An inode is a unique<br>
identifier for that file. Notice that your two files have different
inodes?<br>
<br>
When the loader goes to load code for your two servers using those<br>
files, each is copied in to swap (so your swap space is n servers * sizeof
executable)<br>
The same is true of code segments. <br>
<br>
If you sym link the two executables (Note they must be on the same<br>
filesystem to do so. If you symlink two files on different file systems,<br>
obviously Linux will have to copy the file to the new file system, and it<br>
will have a new inode number. (This is because each filesystem has<br>
it's own superblock, which maps Inodes to file blocks, and file names.<br>
<br>
The filename if only for human consumption. All Linux cares about is that<br>
inode number.<br>
<br>
anyway... If you symlink the two server files, and now do a "ls -li",<br>
notice the inode numbers are the same!<br>
<br>
When you execute the server (with sticky bit on) it is copied to swap, <br>
then pages copied in to ram and executed. When the second server<br>
is executed, even though the file has a different path, it has the same<br>
Inode. The linux kernel looks up the inode, and notes this inode has<br>
the sticky bit set, and in fact that it already exists in Swap. It copies<br>
the pointers to the code segments as I previously mentioned, and<br>
begins execution.<br>
<br>
You ask why?<br>
<br>
Because 10 servers your way will load 10 copies in to swap, 10<br>
copies in to memory, etc. Using the method of symlinks, which<br>
is really nothing more than a link in the super block. The super block<br>
maintains all information about which disk blocks belong tio which<br>
files. For your simlink the new file entry simply gets the same<br>
inode id copied to the table. Same inode, same code... With<br>
shared libraries in memory, for the 10 servers only 1 copy<br>
exists in swap. Only 1 copy exists in memory.<br>
<br>
I hope this is more clear.<br>
<br>
Dr. D<br>
<br>
<br>
<br>
At 02:18 AM 9/25/2004, you wrote:<br style='mso-special-character:line-break'>
<![if !supportLineBreakNewLine]><br style='mso-special-character:line-break'>
<![endif]><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Guess im a little
confuused here, why would you symlink when cod (all quake3 base games) support
multiple users. using fs_basepath and fs_homepath accomplishes the same thing
as symlinking doesnt it?<br>
Jase<br>
NateDog wrote:<br>
<br style='mso-special-character:line-break'>
<![if !supportLineBreakNewLine]><br style='mso-special-character:line-break'>
<![endif]><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Woah......now there's a
guy who knows his stuff! Awesome tips man! You<br>
really explain things well. Much appreciated.<br>
<br>
--<br>
NateDog<br>
<br>
----- Original Message ----- From: Mark J. DeFilippis<br>
To: cod@icculus.org<br>
Sent: Friday, September 24, 2004 9:59 PM<br>
Subject: RE: [cod] Semi off topic: COD rentals<br>
<br>
<br>
<br>
I had written much about this a while back. I will repeat a bit of<br>
it here for the sake of those who wish to do this. Want to know why<br>
you should do this, why it works and a bit on how it works...<br>
<br>
Linking the binaries allows the CPU to share the same Code segment pages.<br>
Servers<br>
will be allocated their own data segments for both Heap and Stack<br>
(Which grow towards one another)... One of the reasons Ryan was able<br>
to so quickly find that original prob back in 1.1.)<br>
<br>
If there is a write attempt to the code segment, that server/user is given<br>
their own copy. In the case of most of the shared libs in Linux, the code<br>
is reentrant, and hence these writes don't happen.<br>
<br>
One other recommendation, I am not certain if I made...<br>
<br>
You can reduce the spikes you get when a server is restarted by<br>
setting the "Sticky" bit on the executable. (Do a man on
"mode" command)<br>
What this does is the first time the executable is loaded, the entire<br>
executable is copies to SWAP space. Once copied to swap, executable<br>
pages are copied in to ram to be executed.<br>
<br>
The best way to keep a server at optimum is to never have to page.<br>
However, under certain conditions, this does happen. It the executable<br>
is sticky, it remains in swap, and the page segment need only be<br>
brought back in to memory from swap.<br>
<br>
Also note, when a second and subsequent user of the Sym Linked executable<br>
starts his/her server, the executable IS NOT copied in to swap again, it<br>
uses<br>
the one already in swap (hence the concept "sticky")... it sticks
there.<br>
<br>
Thus on new startup, A call is made to load the executable, however the<br>
Kernel immediately updates the CS and ES code pointers to the shared<br>
memory mbufs where the executable code exists, allocates a DS data<br>
segment, and moves your process back to the scheduler for CPU as<br>
your I/O is complete.<br>
<br>
You skip the copy of the executable to SWAP.<br>
You skip the copy of pages to Real RAM.<br>
You execute off shared pages in memory already with your own set of<br>
executable<br>
registers CS, ES. Get your data segment, and your server starts
up.<br>
<br>
Not only do you save ram, but start impact on the other servers due to I/O<br>
DMA transfer setup, and context switching between system and user space,<br>
but you spare the CPU spike as well.<br>
<br>
Regards<br>
<br>
Dr. D<br>
<br>
<br>
At 05:08 PM 9/24/2004, you wrote:<br>
<br>
I just had that question recently also. I did some research on the
internet<br>
and a lot of peeps are doing symlinks. I tried it with MOH:AA and it
works<br>
beautifully, not sure if that's the "right" way to do it but it's
pretty<br>
cool cause' you have one base install and symlinks in the other client<br>
folders.<br>
<br>
--<br>
NateDog<br>
<br>
<br>
<br>
<br style='mso-special-character:line-break'>
<![if !supportLineBreakNewLine]><br style='mso-special-character:line-break'>
<![endif]><o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>-----Original
Message-----<br>
From: John Kennington [<a href="mailto:john.kennington@buzzcard.gatech.edu"
eudora=autourl>mailto:john.kennington@buzzcard.gatech.edu</a>]<br>
Sent: Friday, September 24, 2004 3:04 PM<br>
To: cod@icculus.org<br>
Subject: RE: [cod] Semi off topic: COD rentals<br>
<br>
Depending on the number of cpus in the box, you can run 10 to 15 CoD<br>
servers per<br>
box. So it is quite cost effective.<br>
<br>
John Kennington<br>
<br>
-----Original Message-----<br>
From: Jafo [<a href="mailto:jafo@nowhere.ca" eudora=autourl>mailto:jafo@nowhere.ca</a>]<br>
Sent: Friday, September 24, 2004 3:58 PM<br>
To: cod@icculus.org<br>
Subject: [cod] Semi off topic: COD rentals<br>
<br>
Hello,<br>
<br>
If this isn't the forum for this question, please forgive me for asking<br>
here.<br>
<br>
There seems like a lot of people on this list that run "server
rental"<br>
operations. Just curious how people are doing that cost effectively?<br>
Obviously one can't run each customer's game server on seperate hardware.<br>
Are people using some sort of "virtual linux" installs to run
multiple<br>
servers on one box with seperate IP addresses? If that is the case how<br>
many servers would one dual 2.4 Xeon w/2gig RAM run?<br>
<br>
Thanks,<br>
Jafo<br>
<br>
<o:p></o:p></span></font></p>
<p class=MsoNormal style='margin-left:36.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>----------------------------------------------------------------------------<o:p></o:p></span></font></p>
<p style='mso-margin-top-alt:5.0pt;margin-right:0cm;margin-bottom:12.0pt;
margin-left:36.0pt'></x-sigsep><tt><font size=2 face="Courier New"><span
style='font-size:10.0pt'><x-sigsep>S2-------------------------------------------------------------------------------</span></font></tt><font
size=2 face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New"'><br>
<tt><font face="Courier New">Mark J. DeFilippis, Ph. D
EE defilm@acm.org</font></tt><br>
<tt><font face="Courier New">
defilm@ieee.org</font></tt><br style='mso-special-character:line-break'>
<![if !supportLineBreakNewLine]><br style='mso-special-character:line-break'>
<![endif]></span></font><o:p></o:p></p>
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