Hi. I am running Kubuntu 7.04. When I boot my computer and I go to system monitor, it shows about 190Mb of memory used. When I open a browser and a mail client, it goes up to about 250Mb.
Now, I left the computer on and did a few things in the last couple of days. After that, everything was closed except for a browser and the mail client, but now the system monitor shows 800Mb used!!!
It looks like if I did other stuff, even after I closed those applications, the memory is still used. I hated Windows because it becomes slower and slower with time, does Ubuntu do the same????????? How do I clear the memory? Thanks

You don't (need to).

http://gentoo-wiki.com/FAQ_Linux_Memory_Management

I just read another post about more or less the same issue. According to that post, leaving Firefox open for a long time will fill your memory. I am not sure about what this means, but the post referred to firefox as being "leaky". Any help to prevent that?
Also, if I have web sites with flash open, will that fill the memory more? And will all this make the system less responsive? Thanks

Upgrade firefox or change its settings.

If sites have more than one flash animation, Firefox will crawl. Seamonkey, Opera, or Konqueror could be used.

There is nothing to be done unless your computer is visibly getting slower. Read dawkcid's link and pay special attention to swappiness.

I thinnk all the talk about firefox memory leaking is overblown.

If your box is running fine without slowing down due to memory thrashing then all is OK.

Linux is reporting to you virtual memory. All Linux processes think they are the only one and position themselves to use all available memory. Its a feature -- just ignore it.

I think his "problem" is due to the setting of the swappiness variable. I've noticed several posts from ubuntu users lately related to "high memory usage" but no discernible symptoms other than they saw a high figure when they looked at memory usage.

yea swappiness is the weirdest thing. ever since they added the user changeable variable some really funny threads on kernel trap have shown up where the developers can't seem to agree on what the proper behaviour of a desktop machine is.

think of the swappiness variable as (swap) pageout useless anonymous data pages to reclaim memory vs page cache used to reclaim memory space preasure.
the default setting of 60 will prefer to reclaim pagecache, but will have to start swapping at *some* level of reclaim failure. the swappiness value sets that level of failure.

if you have some app eating up memory with anonymous data then swap=100 sounds like the best setting ever


here i think its important to understand that swap "pageout" actually only relates to anonymous memory. apps that get kicked back to disk are in the page cache.

don't be thinking of this like whole apps get "swapped" like it used to be in 1983.

so if you set swap really low like i see in alot of ubuntu discussions you are going to experience latency between apps and your machine might be vulnerable to crashing out of memory.

swap is an important thing so the kernel can properly manage memory. the more swappy the better.
in particular if there are memory leaks in an application. memory leaks by definition create anonymous data that can neven be kicked out without swappiness.