Memory Usage

Hello,

I have a new Linux Server setup and was monitoring the memory usage.
The system is fitted with 1024meg of ram, when first booted it uses about 500meg, then as time passes grows to be using more and more.
Is this normal? Will it stop when it gets close to 1gb?
There is just a webserver & mysql database, no real load.

Thanks Heaps

Rhys

this is standard behaviour. don´t worry. it uses all available memory for caching. if a program will request memory, the OS will free some cache.

OK, Thanks for that,

Just wondering.
What sort of things does it cache?

Thanks

Rhys

afaik it´s inodes from the filesystem.

"top" at the command line will tell you how much is cached. On my boxen (one of which has 2 gig of ram and is a mod_perl/mysql box that sees moderate traffic) it will eat up all the ram, but 70% of the used ram is in the cache.

I think of used cache ram as a good thing, it means your box will be hitting the filesystem far less than it would without it. As I understand, cached ram can be dropped immediatly and freed up if your box needs it.

What this comes down to: using up your ram and putting things into cached ram is expected, and desirable, behavior.

Exactly, cached RAM is a good thing. You experience essentially no performance hit in simply removing it from the used pages table if you need to free up that spot in RAM, but if you end up needing it (and the kernel uses a somewhat sophisticated algorithm for aging cached pages so that ones that you are less likely to need expire first) then you get a major performance gain by not having to access the disk at all.

Just like processor L1 and L2 cache, the more stuff you can have in cache and can get through cache hits .. the better.

[OT]
I'm using 512 RIMM (the server hardware is just ready, tommorow will be install time) for my webserver (Low-end PHP/MySQL use mostly).

The board can handle up to P1066 RIMM, but I could't find any 512 mb P1066 RIMM chips (only P800) so I chose two 256 mb 1066 chips.

What do you think, is what is 512 mb 1066 RIMM compared to a. 1024 mb DDR b. 1024 mb SDRAM c. 1024 mb RIMM P800?