topic Re: memory usage in Operating System - Linux

memory usage

Vijaya Kumar_3 — Thu, 13 Nov 2003 11:01:05 GMT

I have a linux system with 4 gigs of memory and after installation i found i am getting only 1 gigs for applications...
here is my vmstat output:

r b w swpd free buff cache si so bi bo in cs us sy id
0 0 0 17068 988120 145884 2605204 0 0 1 3 4 5 1 0 0

Some one tell me how can get the cache memory back to my applications...

Here is my top output:
Mem: 3947940K av, 3458628K used, 489312K free, 0K shrd, 146032K buff
Swap: 1048552K av, 17068K used, 1031484K free 2605208K cached

Thanks
Vijay

Re: memory usage

Claudio Cilloni — Thu, 13 Nov 2003 11:20:52 GMT

I'm not so sure... but having 1GB of swap space could limit your application memory space to 1GB.
Try adding some swap space using files, It's easier. Just to make a test...

hth,
Claudio

Re: memory usage

Huc_1 — Thu, 13 Nov 2003 11:29:18 GMT

Maybe at startup it is not seen

check in dmesg if you see 4G

if not have alook at

/usr/src/linux-2.4.20-20.9/Documentation/kernel-parameters.txt

in there you will find how to pass this to kernel as parameter at boot

look for parameter mem=

after you have tested this works do not forget to make it permanent from lilo or grub

# meminfo

also help to see memory informations

J-P

Re: memory usage

Steven E. Protter — Thu, 13 Nov 2003 11:50:45 GMT

You might need to install and start using the Red Hat/your vendor bigmem kernel.

This kernel is designed for systems with memory in excess of 2 GB.

Also, swap on most Linux/Unix systems needs to be at least half of system memory. That's fur sure on HP-UX and a rule I've seen in Linux guides.

sEP

Re: memory usage

Vijaya Kumar_3 — Thu, 13 Nov 2003 12:10:35 GMT

good point Steve and Huc...

Here is my GRUB line for kernel:

kernel /boot/vmlinuz-2.4.16-WSPACK ro root=/dev/cciss/c0d0p1

I think it is not enabled with bigmem...

am i right?

-Vijay

Re: memory usage

Martin P.J. Zinser — Thu, 13 Nov 2003 12:11:33 GMT

Do a grep GB .config on your kernel sources. That should tell you how your kernel was build.

Re: memory usage

Steven E. Protter — Thu, 13 Nov 2003 12:24:44 GMT

If you can boot your system and look at the console.

All installed and configured kernels will show on the startup screen on the console.

If you see one called bigmem, choose it with the keyboard and see if it boots.

If its not there, go get one from Red Hat. Its an rpm file and pretty easy to install either from the command line or Red Hat Update.

The default line of the grub file tells the system which kernel to auto boot.

Don't delete the old kernel while running this experiment. Make sure the new one works and gives good results before making any changes.

SEP

Re: memory usage

Huc_1 — Thu, 13 Nov 2003 12:30:40 GMT

Martin is right do a grep "GB" on the .config file for your kernel

also at the top of your dmesg you will see how much is seen at boot

# dmesg | less

if this is not your total and your .config say somrthing like

------------
grep "GB" /boot/config-2.4.20-20.9
# CONFIG_3GB is not set
# CONFIG_2GB is not set
CONFIG_1GB=y
------------

then you are right, you dont have the bigmem

J-P

Re: memory usage

Vijaya Kumar_3 — Thu, 13 Nov 2003 12:31:08 GMT

Thanks Martin and Steve

I checked my .config in /usr/src/linux but no luck with "grep GB .config" (no output)

How can check my running kernel is supporting big memory more than 2GB...

Thanks
Vijay

Re: memory usage

Vijaya Kumar_3 — Thu, 13 Nov 2003 12:33:40 GMT

Oh... i forgot to test dmesg...the system finds 4 GB during boot....

Memory: 3947712k/4014056k available (1857k kernel code, 65956k reserved, 558k data, 228k init, 3096
552k highmem)

Now the issue is my application is using only 1 Gigs...any reasons

-Vijay

Re: memory usage

Steven E. Protter — Thu, 13 Nov 2003 12:35:53 GMT

I'll need a hint to answer your last question.

What application is it?

Who is the vendor?

If I know anything about it, I'll try and help. If not, you may need to contact the vendor of the application.

SEP

Re: memory usage

Stuart Browne — Thu, 13 Nov 2003 21:00:40 GMT

What I find intersting is these numbers:

> Mem: 3947940K av, 3458628K used, 489312K free, 0K shrd, 146032K buff
> Swap: 1048552K av, 17068K used, 1031484K free 2605208K cached

Sure 4GB found. 3.4GB used. 2.6GB of disk chaching.

It honesly lookslike it's being used, and there's 500 or so MB available.

Looking deeper into /proc/meminfo would give more details.

If I had to guess, I'd say big-scale databases were at work here, to cause that level of cache. Oracle? DB/2?

Doesn't appear to be all that much user-space memory usage.

Re: memory usage

Ragu_1 — Thu, 13 Nov 2003 21:23:11 GMT

My wild guess is that your application is behaving erratically. Can you ping the forum on how much buffered RAM is getting eaten away once you start your app ? `free' is your friend . If possible fall back to the version of glibc suggested by the app vendor.