Re: [aclug-L] Kernel/Memory Question!!

[John Goerzen <jgoerzen@xxxxxxxxxxxx>]

On Sun, Jan 17, 1999 at 11:17:55PM -0600, Mohammad Islam wrote:

> Anybody out there running RH5.1(Kernel2.0.34) having memory consumption
> problem? I happend to issue a "free" command today and was surprised to
> see about 71M of memory used out of 80M on my system.

That can be misleading; here's the output on my system:

erwin ~$ free
             total       used       free     shared    buffers     cached
Mem:        256872     251552       5320      52704      40200      94896
-/+ buffers/cache:     116456     140416
Swap:       130160        600     129560

What Linux does is try to use as much memory as possible, rather than
letting memory go to waste.  If you do not have applications using all of
your memory, then it will use the remaining memory for disk cache.  At the
moment I issued that command, it was using 94 megs for disk cache and 40
megs for buffers.  That is why it reports only 5 meg free -- because it
automatically uses spare memory for something useful.

If you look at the second line, this shows the values in terms that you are
more used to seeing in other operating systems.  It adjusts the figures to
ignore the buffer/cache systems, and shows that I have 140 megs of memory
available should I need it.

> 1.Anybody aware of any memory leaks on kernel 2.0.34?

That is possible; it would be good to upgrade to 2.0.36 anyway.

> 3.Where can find kernel related bugs/fix info/docs?(Any central site
> that zeroes in on   kernel only?)

www.linuxhq.com, "kernel patches" section under the stable release area has
changelogs.

> 4.Can anyone provide some insight about reading/understanding memory  
> usage/tweaking/optimization on Linux?

There generally isn't much to tweak beyond setting up swap partitions; the
system adapts to current conditions fairly well.  If you think about it a
minute, you realize that this philosophy makes a lot of sense.  Other
DOS-based OSs (including 95/98) will just sit there and let vast amounts of
memory do nothing, whereas Linux will put it to good use when it's not
needed by some other program.  And, of course, when you fire up a large
program, Linux will automatically shrink its cache so that the program can
use the memory without any swapping.

John

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