Absolutely right. The first mistake that most people make when looking at any perf problem is to say 'all my memory is in use, that's my problem' when all that is just a symptom of linux using RAM aggressively to cache buffers.

Equally, note that having a substantial portion of your swap used doesn't slow you down, per se. What slows you down is traffic to and from the swap file (so if you have 500 megs of swap in use that doesn't make the machine slow necessarily, but if your machine is continuously moving pages to and fro between the swap file, that does slow you down - and both of the two cases may have similar amounts of swap in use, but one has traffic and the other doesn't).

So, I'm going to suggest that you do something very low tech: Look at the hard drive light. Is that continually flashing, even when you are not doing anything obvious (explicitly opening and closing files) to cause it?

BTW, I am currently having a similar problem on a (k)ubuntu box. When 6.06 was originally installed it did not have this problem, but somewhere along the line the problem has started. I think some update has given me a memory leak, which means that slowly 'dead' pages accumulate in memory which eventually leads to performance becoming non-existant. Not ideal. A reboot always cures it.

I first noticed this problem when I started using Opera's RSS client (and when that's got several thousands of items it seems a bit inefficient with memory). I've changed to using kde's akregator and that seems to have alleviated the problem somewhat, and changing to firefox seems to be a bit better too. My feeling however was that in the underlying infrastructure, some library was actually leaking - the suggestion that it might be x.org is interesting and one I hadn't thought of. I seem to be running x.org 7.0.0.

Because I've changed major apps completely (& given up using OO on this box - even if open Office has no memory leaks, it is undoubtedly big, and big makes the problem worse), I don't think that it is a memory leak within an app itself, but somewhere in the underlying infrastructure.

I've tried setting 'swappiness' down to a lower value, and while that makes the box a little snappier when it first boots, I'm not convinced it does anything about the long term slow down. It may even make things worse when the box really bogs down.

I am guessing you are talking about swap activity. As jiml8 pointed out in post #4 you can quantify that with the output from vmstat. (And avoid potentially confusing swap activity with file access.) W/o parameters, it will give the average rates of swapping in and out (see man page for units.) You can also have it repeat output at intervals. In which case after the first line, each output reflects what happened during the just elapsed interval. My rule of thumb is that if the swap rates are a small fraction of the possible disk throughput, there is probably not an issue.

BTW, somehow I missed the activity that happened on this thread on Jul 29. In post #2 I was fishing for possible causes. The reason I asked for the output of df was to make sure a clogged disk partition wan't causing the problem. (I don't know that it could, but I was trying to cast a wide net.) Now it is obvious there is no issue with disk space.

hmm i am having similar problems like this with xorg swallowing masses of ram on fedora 7. using fglrx driver however if this makes a difference. i have noticed that openoffice does also use an incredible amount of ram also. having a couple of documents open with embedded pictures makes it use 480m of ram with xorg using another 400ish that doesnt leave alot left for the system. does xorg amass the combined memory usage of all x11 programs or something?

My experience is that as additional windows are opened, X will consume more RAM. I am guessing this is basically where it "draws the pictures." I have a system that is a bit starved for RAM. As a result, it is normal for a significant part of X to be swapped. For example, right now, X has aprox 21 MB resident and 22 MB swapped. This shows up sometimes when I switch desktops (workspaces) where it takes a couple of seconds to repaint the screen.

I am just surmising from my experience. I have not looked at X source code.

(BTW, I would not think of trying to open OpenOffice.org on this RAM starved machine! I leave that for machines that were actually made this century. )

433920k of that is disk cache

Keith