screwy mandrake memory problems..

[VHockey86]

Maybe I'm totally off here.. but isn't linux supposed to be very good at managing memory? Im wondering if I have something setup wrong, because when I startup my system there is about 300MB or 512 RAM free... and after about 30 mins to an hour of casual use (instant messaging, listening to mp3s), the thing is out of memory.

take a look at these pictures for a better idea:
Fresh Startup:

http://www.netsync.net/users/drpmkp/freshboot.jpg

A little later:

http://www.netsync.net/users/drpmkp/30mins.jpg


Also, how come linux does use any of the allocated swap space?
I thought Swap space is where something like disk cache would go?

[krohnjw]

Ok, what you are missing here is how linux USES memory.

Linux is very aggressive about placing unused memory into a cache so that it can access it quicker and use it better. If you look at that picture you will see that under 30% of your actual memory is used, the rest is cached for use, still free for programs to use, just ready to be accessed in an efficient manner.

It will not touch your swap partition until you are using a good amount of physical memory, which makes sense as disk access is significantly more costly than main memory access.

That isn't a memory problem, that is efficient use of memory by a kernel

[SpookyEddy]

^^^ what krohnjw said. No point in having perfectly good RAM sat around doing nothing when it can just as well be used for caching data you are quite likely to use again at some point.

Heres a snapshot of the memory usage on my machine (2.6.3 kernel and 768MB of RAM) while its sat at idle with a few apps open, you will notice that I only have 10 meg free...

Slacker:/etc# free -m
             total       used       free     shared    buffers     cached
Mem:           756        746         10          0        100        293
-/+ buffers/cache:        352        404
Swap:          486          0        486

Swapping to disk is best avoided if you have plenty of free memory to use for caching.

The system is not "out of memory", its just attempting to use any free memory it has available to it for something constructive... IMO a sensible piece of memory managment.

Regards

ed

[VHockey86]

k, thx for the explanation. I noticed that when it does get that low it tends to slow down opening programs and such, but still not too terrible.

[krohnjw]

It shouldnt slow the opening of programs at all, I would guess this is a spurrious correlation, as you still have over 70% of your system memory free.

[SpookyEddy]

Infact if anything it should speed up some tasks. Just out of interest what kernel version are you running (memory managment, among other things, has seen some fairly radical reworking over the last year or so)?

[VHockey86]

um, not sure on the kernell version (nor how to find it out, I'm a noob at linux). I'm running Mandrake 9.2 that I downloaded last december or november

[krohnjw]

uname -r

AFAIK that is a late 2.4 kernel, so memory management should be fairly mature and reliable

[VHockey86]

2.4.22-10mdk