How to remove cached memory?

Thank you for a speedy answer =)

But I am using the web-interface alot, to change and monitor the PBX, so I cant really turn off Apache, can I? And the same with the FOP, if the flash panel is in use, you kinda need the script I assume?

What I was thinking of, was some way to flush (or dump or whatever) that which has been cached, so I can free up memory, say, every night or so? I can't really tell which program it is that is doing all this caching, is it asterisk, apache, linux or perhaps all of them...?

It is just something that I want to be able to experiment with, to see if it might have a positive impact on performance. It probably wont, but I want to learn more and experiment with this, so I would appreciate all the help I can get.

I have tried to restart Asterisk, Apache and MySQL now, and nothing frees up any memory. The 256MB machine is now at 99% used memory constantly. Any ideas as to how I can free up some? 37% of it is cache, this has to be dumpable in some way...

--Thomas

Edit: I tried some more, and restarting Apache does free up some memory. However, this is just ordinary physical memory, the cached part stays the same. Apache also quickly consumes up the memory it released on restart...

What is this cached memory exactly? Which program is it that Caches it, and how can I control it?

Yeah, thanks. Thats exactly how i feel.

I have been looking around alot, but i cant seem to find anything on this. The problem here is that I am planning on running several applications on my PBX, not just asterisk. I figured that it might work fine for trixbox to run on 99% used memory all the time, but when installing other programs, there might be some problems. There probably wont be any, but I want to be prepared, just in case.

I'm not sure what you're referring to when you say "the memory bar turns red" but I can assure you that Linux uses cache efficiently.

Look at it this way: if you're not doing anything with your RAM, why shouldn't the system use it to cache? The cache gets low priority, and gets overwritten with any "real" data without any extra effort (the caching is part of the kernel -- unless you compile it out (and I don't even know if that's possible) it's not going to stop.)

Now that I've said that, what exactly do you mean when you talk about "the red bar?" If you're having issues with RAM capacity and you have 512MB or more then there certainly may be something wrong with your setup.

To re-iterate, it's normal and desired for your RAM to be 90%+ used in Linux. The time to start worrying is if there is excessive swap, or (IMO) any swap on a telecom system. Add more RAM and remove unneeded services. :)

This link has a capture from the Admin mode of my Trixbox. It clearly shows the Memory Bar in the Red. This is what alarms me. If everything is OK it should be Green all the time. http://bellsouthpwp.net/e/s/eselliso/trixbox.jpg

I have the same request - is it possible to flush the cache without rebooting.

Haha, ok, I see what you guys are fussing over.

In that particular picture you do not have an issue. You are using 0 swap. Whoever coded that app made a mistake making the memory red, because a Linux system will always, always, always use as much RAM as it can for cache. You can safely ignore this, and you might even consider filing a bug or pestering kerry and/or andrew.

You're only using 33% of your "real" RAM. That and the amount of swap being used are the only things to be concerned with.