I found that linux use a lot of memory in disk cache. After running for awhile, linux start to use sap disk space and I don't like that. Can I set maximun cache size to limit the size of disk cache?

You should be able to locate it
in the kernel sources ... there's no
"more end user like" way to do it.

However, your should trust Linux.
It's memory utilisation is unsurplused :)

It will swap out processes that are inactive
for a long time, no matter how much RAM
you have, and it really does make sense.

Cheers,
Tink

1 members found this post helpful.

oh, thanks. That mean I shouldn't do it now. I would like to have about 20MB of free ram so some applications might startup faster. Anyway, switch from kde to xfce already help a bit.

I know this post it old but since I found it while looking for something else it means other people will find it as well so I thought I would post some corrections.

There is a "more end user like" way to handle this and it's there because how it is designed in the kernel sources is implemented as what is the assumed best for each user but for a lot of people this isn't the best. Sun (now Oracle) in fact suggests ways to tune the VM (Virtual Memory) usage on Linux for when you install items such as their databases but this can apply to all sorts of things. Also, not everything I suggest had the same option when these posts were submitted however they were available under different names.

To change how much the swap is used, run: sysctl -w vm.swappiness=X
replace X with an int between 0 and 100. 0 means only use swap when their are no other options and 100 means use swap as often as possible.

To make sure you always have X amount of Ram available (in kilobytes), run: sysctl -w vm.min_free_kbytes=X

To empty the page cache and the dirty write buffers with all committed transactions, run: sync && sysctl -w vm.drop_caches=3

vm.drop_caches is a command and not a tunable however the other ones can be stored in /etc/sysctl.conf and automatically set each time the system boots. There are many more options to explore for tuning VM and I would encourage you to read sysctl/vm.txt.gz in the Linux kernel source Documentation folder.