We're testing an implementation of vbulletin on a Cobalt Raq 4i with 256mb RAM. This is the only domain on the server:

40 users on the board. Load .53 .58 .50 <---- this looks good, right?

Physical memory used - 167mb <---- what the???

Is this memory usage anything to worry about? I mean, am I going to have to have 256mb for every big vbulletin installation?

Thanks.

If you have 40 users on the board at one time, thats about right. Load time look good, memory, well bb's take up alot of memory, also it might not really be using that much memory it may have some set aside for use later.

Physical memory used - 167mb <---- what the???

If this is out of 256, I would highly recommend another 256. It is cheap right now. One of these times, your box will spike and die. The more RAM the better.

Don't waste that RAM
Linux uses memory very efficiently. Generally, Linux, when running web servers, databases and other such daemons, will use almost all of your physical RAM regardless of how much you install. Of course, once you get over the 512MB range, relative usage will be less.


:confused:Newbies Error
Many Linux users are suprised when they install more RAM into their machines and find that most of the new RAM is used immediately. This does not necessarilly mean your machine was starving for RAM. If your machine has been tweaked for multimedia, file i/o or high speed networking, then a lot of your memory is probably being used for buffers and the file cache. I have seen people put in a 128MB stick (back when it wasn't so cheap), then add another stick -- only to see all of the new 256MB used up. Don't make this mistake.

Buffering and Caches
Linux uses disk caching, buffering and other memory management techniques very effectively. So, often times, linux will be using (more like reserving) almost all of your physical RAM, but when a process needs more RAM, the system will give up the resources to the process.

A key thing to watch is the use of swap space. If your physical memory is >95% used and you are using a considerable portion of your swap space, then you have RAM issues. Try adding more RAM. With RAM prices as they are, go for 256MB or 512MB sticks. This will prevent you from having to throw out 128MB sticks to update RAM when all of your slots are full.

:cool:Use the free command.
Run the "free" command and you will see some memory usage info:


total used free shared buffers cached
Mem: 127868 121752 6116 108164 13184 66808
-/+ buffers/cache: 41760 86108
Swap: 131532 4240 12729


This is a Raq with only 128MB of RAM. You can see nearly all of the physical memory is used, but notice the amount used for cached files (66MB) and for buffers (13MB). Most importantly, notice the -/+ line. This is the amount of memory available -/+ the buffers. Notice buffers+cache+free equals the amount undre the -/+ line. In this example there is 86MB of free physical RAM available. Look at the man pages for free for more options.

:unhappy:Caches are important
On web servers, caches are important. If the program does not manage its own caching, then the linux file cache will help out. There are tweaks for web servers, database, and fileservers to up the default amount of memory used for file caches. These are helpful in speeding up response times without having to use a special cache system. If you do not have enough RAM for caches, all content request will have to go to the disk to get the file, thus making you and your web surfers unhappy.

Be Pragmatic
RAM is getting cheap. A 512MB ECC PC133 DIMM can be had for around $100. If you can add RAM to your box, now is a good time to do it. Usually, RAM cannot hurt and may solve problems for you. However, if your dedicated server provider charges your monthly for additional RAM, then some of the info above might save you a buck or two (which you are free to mail to me at your leisure ;) )


=========
edited to correct an error

Thank you for the very informative replies!!!! I really appreciate it.

If my provider (Rackshack) weren't so darn high when it comes to additional ram (can you believe $29 setup and $79 monthly for a 512MB upgrade?!!?!?) I'd bump it all the way to a gig!

Thanks again.

thats rackshacks biggest downside. The monthly charge for ram. But I guess that must be how they make their money back ... since they are so cheap:)

David

Originally posted by captnroger
I'd bump it all the way to a gig!

Not on a RaQ you wouldn't...

Originally posted by Chicken


Not on a RaQ you wouldn't...


hehe

Originally posted by huck

total used free shared buffers cached
Mem: 127868 121752 6116 108164 13184 66808
-/+ buffers/cache: 41760 86108
Swap: 131532 4240 12729
[/code]

This is a Raq with only 128MB of RAM. You can see nearly all of the physical memory is used, but notice the amount used for cached files (66MB) and for buffers (13MB). Most importantly, notice the -/+ line. This is the amount of memory available -/+ the buffers. Notice buffers+cache+free equals the amount under the -/+ line. In this example there is 41MB of free physical RAM available. Look at the man pages for free for more options.


Just a small correction as far as the -/+ buffers/cache explanation goes:
The amount of used memory in you example is 41Mb, and the amount of " free physical memory is 86Mb.

From the man pages:
"The -o switch disables the display of a "buffer adjusted" line. Unless specified free subtracts/adds buffer memory from/to the used/free memory reports (respec*tively!). "

But thanks for posting this, I was ready to order a memory upgrade myself, but it appears as if it is not quite necessary.

The RaQ is "using" between 90-95% of memory according to "top":


Mem: 128040K av, 121572K used, 6468K free, 116892K shrd, 23160K buff
Swap: 131532K av, 7744K used, 123788K free 40348K cached

whilst "free" shows this:
total used free shared buffers cached
Mem: 128040 121464 6576 116568 23160 40348
-/+ buffers/cache: 57956 70084
Swap: 131532 7744 123788


The above was edited after Huck posted his formatting hint ;-)

Rgrds,

Johan

Just a tip....
when you copy stuff from your command line use the code option designated by the # sign above. This will force the board to show your post in a font face with fixed spacing ... thus making it much easer to read.


with code tags



total used free shared buffers cached
Mem: 127868 121752 6116 108164 13184 66808
-/+ buffers/cache: 41760 86108
Swap: 131532 4240 12729



without code tags

total used free shared buffers cached
Mem: 127868 121752 6116 108164 13184 66808
-/+ buffers/cache: 41760 86108
Swap: 131532 4240 12729

If you are a rackshack customer they offering a "special" upgrade for 39 bux 1 time fee for 128 stick of mem..

Originally posted by huck
Just a tip....
when you copy stuff from your command line use the code option designated by the # sign above. This will force the board to show your post in a font face with fixed spacing ... thus making it much easer to read.


Thanks ;-)

Johan