[cod] Semi off topic: COD rentals

Jafo jafo at nowhere.ca
Mon Sep 27 09:42:26 EDT 2004


Hello everyone,

Thanks to everyone who responded to this thread! I was really expecting
hosting companies to be pretty closed lipped about this! Picked up some
REALLY good information from people's posts thank you very much!

I'm going to purchase a box, co-lo it and get things started!

I never even thought about running one set of binaries with virtual
interfaces, that really beats virtual OS installs! Not to mention the
gains by running one set of binaries with sticky bit set!

Mark, you provided some really good in depth feedback, I really appreciate
it!

Thanks all,
Keith.

On Sat, 25 Sep 2004, Mark J. DeFilippis wrote:

>
> If you are executing the same executable and can use parameters on the
> command line that is
> fine.  It is the same inode.  The question I was answering was for a person
> who appeared to
> not understand why, if Linux is in fact a multiuser/multi-tasking OS, what
> difference does
> it make if I load from one file or many copies of the file.
>
> In the scenario you present... if you are executing the same file, it is
> the same
> inode.  Make it sticky... and you have the same as the symlink scenario.
>
> For those admins that wish to have a separate executable in the user
> space (on perhaps a server where the admin choose to have the executable
> in the users space with his other files and configs)  the symlink method works
> very well.
>
> If your servers are being spawned by calling the same executable, you in fact
> are correct, you get the same benefits. For added savings on load, make the
> executable
> sticky, and your golden.
>
> Dr. D
>
>
> At 03:51 PM 9/25/2004, you wrote:
>
> >But we execute the same binary in the same path for each server&? Why the
> >symlink?
> >
> >
> >
> >------------------------------------
> >
> >Chris Adams
> >
> >Fragzzhost
> >
> >
> >
> >T (07005) 964 855
> >
> >F (07005) 964 857
> >
> ><http://www.fragzzhost.com>www.fragzzhost.com
> >
> >
> >
> >-----Original Message-----
> >From: Mark J. DeFilippis [mailto:defilm at acm.org]
> >Sent: 25 September 2004 20:33
> >To: cod at icculus.org
> >Subject: Re: [cod] Semi off topic: COD rentals
> >
> >
> >
> >
> >You are thinking application level.  This is Kernel level.
> >I spent lots of time in my career developing real time embedded coding
> >in Unix/Linux kernels.
> >
> >Look at two linuxded files that are not sym linked. But use this:
> >
> >ls -li
> >
> >Note the left side has a value called an inode.  An inode is a unique
> >identifier for that file.  Notice that your two files have different inodes?
> >
> >When the loader goes to load code for your two servers using those
> >files, each is copied in to swap (so your swap space is n servers * sizeof
> >executable)
> >The same is true of code segments.
> >
> >If you sym link the two executables (Note they must be on the same
> >filesystem to do so. If you symlink two files on different file systems,
> >obviously Linux will have to copy the file to the new file system, and it
> >will have a new inode number.  (This is because each filesystem has
> >it's own superblock, which maps Inodes to file blocks, and file names.
> >
> >The filename if only for human consumption.  All Linux cares about is that
> >inode number.
> >
> >anyway... If you symlink the two server files, and now do a "ls -li",
> >notice the inode numbers are the same!
> >
> >When you execute the server (with sticky bit on) it is copied to swap,
> >then pages copied in to ram and executed.  When the second server
> >is executed, even though the file has a different path, it has the same
> >Inode.  The linux kernel looks up the inode, and notes this inode has
> >the sticky bit set, and in fact that it already exists in Swap. It copies
> >the pointers to the code segments as I previously mentioned, and
> >begins execution.
> >
> >You ask why?
> >
> >Because 10 servers your way will load 10 copies in to swap, 10
> >copies in to memory, etc.  Using the method of symlinks, which
> >is really nothing more than a link in the super block.  The super block
> >maintains all information about which disk blocks belong tio which
> >files.  For your simlink the new file entry simply gets the same
> >inode id copied to the table.  Same inode, same code... With
> >shared libraries in memory,  for the 10 servers only 1 copy
> >exists in swap. Only 1 copy exists in memory.
> >
> >I hope this is more clear.
> >
> >Dr. D
> >
> >
> >
> >At 02:18 AM 9/25/2004, you wrote:
> >
> >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?
> >Jase
> >NateDog wrote:
> >
> >
> >Woah......now there's a guy who knows his stuff!  Awesome tips man!  You
> >really explain things well.  Much appreciated.
> >
> >--
> >NateDog
> >
> >----- Original Message ----- From: Mark J. DeFilippis
> >To: cod at icculus.org
> >Sent: Friday, September 24, 2004 9:59 PM
> >Subject: RE: [cod] Semi off topic: COD rentals
> >
> >
> >
> >I had written much about this a while back. I will repeat a bit of
> >it here for the sake of those who wish to do this. Want to know why
> >you should do this, why it works and a bit on how it works...
> >
> >Linking the binaries allows the CPU to share the same Code segment pages.
> >Servers
> >will be allocated their own data segments for both Heap and Stack
> >(Which grow towards one another)... One of the reasons Ryan was able
> >to so quickly find that original prob back in 1.1.)
> >
> >If there is a write attempt to the code segment, that server/user is given
> >their own copy. In the case of most of the shared libs in Linux, the code
> >is reentrant, and hence these writes don't happen.
> >
> >One other recommendation, I am not certain if I made...
> >
> >You can reduce the spikes you get when a server is restarted by
> >setting the "Sticky" bit on the executable.  (Do a man on "mode" command)
> >What this does is the first time the executable is loaded, the entire
> >executable is copies to SWAP space. Once copied to swap, executable
> >pages are copied in to ram to be executed.
> >
> >The best way to keep a server at optimum is to never have to page.
> >However, under certain conditions, this does happen.  It the executable
> >is sticky, it remains in swap, and the page segment need only be
> >brought back in to memory from swap.
> >
> >Also note, when a second and subsequent  user of the Sym Linked executable
> >starts his/her server, the executable IS NOT copied in to swap again, it
> >uses
> >the one already in swap (hence the concept "sticky")... it sticks there.
> >
> >Thus on new startup, A call is made to load the executable, however the
> >Kernel immediately updates the CS and ES code pointers to the shared
> >memory mbufs where the executable code exists, allocates a DS data
> >segment, and moves your process back to the scheduler for CPU as
> >your I/O is complete.
> >
> >You skip the copy of the executable to SWAP.
> >You skip the copy of pages to Real RAM.
> >You execute off shared pages in memory already with your own set of
> >executable
> >   registers CS, ES.  Get your data segment, and your server starts up.
> >
> >Not only do you save ram, but start impact on the other servers due to I/O
> >DMA transfer setup, and context switching between system and user space,
> >but you spare the CPU spike as well.
> >
> >Regards
> >
> >Dr. D
> >
> >
> >At 05:08 PM 9/24/2004, you wrote:
> >
> >I just had that question recently also.  I did some research on the internet
> >and a lot of peeps are doing symlinks.  I tried it with MOH:AA and it works
> >beautifully, not sure if that's the "right" way to do it but it's pretty
> >cool cause' you have one base install and symlinks in the other client
> >folders.
> >
> >--
> >NateDog
> >
> >
> >
> >
> >
> >-----Original Message-----
> >From: John Kennington [mailto:john.kennington at buzzcard.gatech.edu]
> >Sent: Friday, September 24, 2004 3:04 PM
> >To: cod at icculus.org
> >Subject: RE: [cod] Semi off topic: COD rentals
> >
> >Depending on the number of cpus in the box, you can run 10 to 15 CoD
> >servers per
> >box.  So it is quite cost effective.
> >
> >John Kennington
> >
> >-----Original Message-----
> >From: Jafo [mailto:jafo at nowhere.ca]
> >Sent: Friday, September 24, 2004 3:58 PM
> >To: cod at icculus.org
> >Subject: [cod] Semi off topic: COD rentals
> >
> >Hello,
> >
> >If this isn't the forum for this question, please forgive me for asking
> >here.
> >
> >There seems like a lot of people on this list that run "server rental"
> >operations. Just curious how people are doing that cost effectively?
> >Obviously one can't run each customer's game server on seperate hardware.
> >Are people using some sort of "virtual linux" installs to run multiple
> >servers on one box with seperate IP addresses? If that is the case how
> >many servers would one dual 2.4 Xeon w/2gig RAM run?
> >
> >Thanks,
> >Jafo
> >
> >
> >
> >----------------------------------------------------------------------------
> >
> >S2-------------------------------------------------------------------------------
> >Mark J. DeFilippis, Ph. D EE          defilm at acm.org
> >                                       defilm at ieee.org
> S2-------------------------------------------------------------------------------
> Mark J. DeFilippis, Ph. D EE          defilm at acm.org
>                                        defilm at ieee.org
>
>
>




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