Hello,
Since the system slowdown just started becoming apparent, I opened KinfoCenter.
(see attachment screen shot of KinfoCenter)
When I hover the mouse cursor over the Disk Cache memory, the note suggests that it sould be a high number relative to the Physical memory usage.
This does not appear to be the case.
Free Physical Memory (at this moment) 59% 623,403,008 bytes= 594.2 MB
Disk cache 22% 233,201,664 bytes= 222.40 MB

Should I alter Disk Cache usage parameters?
If so, how do I do this?
M

Attached Thumbnails

 

You have a lot of free physical memory and don't need to swap anything on the hard disk so that's not a memory problem and you won't do anything good altering disk cache parameters.

I would use the 'top' command instead to see which processes use a big % of the CPU.

Hello Didier Spaier,
I will look at 'top' again when the system behaves sluggishly.
Right now, there are only a few processes running and firefox-bin uses around 9%, the next highest is Kicker at 1.7%, and then x at 1.5%.

The reason I asked is because there is a tip when the cursor is hovered over the Disk Cache frame in the KinfoCenter. It suggests that when there is a small amount of free physical memory and a large amount of Disk Cache memory, that the system is well configured.
What does that mean?
M

Disk cache (well, as I understand it anyway!) refers to the small amount of cache memory on the hard disk that is used to speed up access. See these 2 short articles that explain what disk cache is:
http://www.webopedia.com/TERM/D/disk_cache.html
http://www.storagereview.com/map/lm.cgi/buffer

Well, size of disk cache memory is only one among many parameters you can fiddle with to increase your overall system speed.

Even experts don't agree about the "good" settings, see this discussion for instance.

So I wouldn't pay too much attention to the tip displayed by kinfocenter.

What is more important is simply have enough RAM in order to minimize swap usage, which is costly in terms of performance. As you had 100 % free swap space at time of taking the snapshot, so far so good.

You can tune your hard disk settings if needed using hdparm. Read carefully the manual before proceeding: 'man hdparm'.

But again, on my laptop at least, stress on the CPU is more likely to cause a slow down of the system, hence my advice to look at 'top' first.

Other than that you can try to adjust some configuration settings in your kernel, see this article from Alien BOB.

Try copying gigabytes of files to an external drive; e.g., back up your home directory with rsync to another drive. You will see disk cache trying to utilize almost all your memory. "Disk cache" is a buffer in RAM for your hard drive. The "disk buffer" is a buffer built-in to your hard drive.

Disk cache won't utilize most of the RAM at all times because the memory controller allocates physical memory on a first come, first serve basis. It's no big deal that sometimes disk cache isn't using much.

See if you can find a package for latencytop. No sense chasing (irrelevant IMHO) side issues - find out where the latency really is. If any.