Red Hat

Hi

I am running in Issue that my total system RAM is 8GB. If I run command

Code:

free -m   I get 6.0 Gb RAM 
free -m
                 total       used       free     shared    buffers     cached
Mem:          7554       5928       1626          0        123       4798
-/+ buffers   1006       6548
Swap:         1996          0       1996

Where as TOP command shows only procesess using 10% of RAM that is 1 GB. Now I read different blogs and understood that cache is also available RAM.

Then I tried to remove cache by ../cache_drops but RHEL3 dont support this command.

Keeping this in mind I allocated 4GB more to Apache Tomcat. Then I started but Tomcat failed to get this much memory. Although this should be free RAM.

I want to know how I can get rid of this CACHE and get memory to RAM.

Br
Osama

The caches are a temporary saving place for files read, since it's faster to access than disk I/O. The system will free it as needed, but if you want to drop the caches now (for whatever reason) run

Code:

echo 3 > /proc/sys/vm/drop_caches

as root. It's only a temporary solution, tho, since you can't disable the mechanism.

As for your Tomcat problem: Since RHEL3 is rather old, I'm guessing you're running on an 32bit platform? That would mean that while the kernel can see more that 4GB RAM, each process can address 4GB total maximum.

Thanks for reply.

RHEL 3.0 dont support the drop_cache command.

For tomcat I was saying regarding OPTs memory ... If this cache memory can be allocated to any other application then why TOMCAT while running says out of Memory error. Because Server has no memory to use.

Please give me suggestions for RHEL3.0 ... kernel 2.4...

There is plenty of memory free based on your free output. You look to have about 7GB free.

It all speaks to how the kernel utilizes memory. Free memory just doesn't sit there. The kernel uses it for "buffers and cache" to speed up performance. think of it as "read ahead" on a drive. The memory is dynamic so if an application need the memory, the cache is quickly cleared and memory is utilized for the application. So take your free # from the mem line and the free # from you buffers line and you have the total free memory on the system.

Now, no application on a 32 bit system can not utilize more that 4GB of RAM. It is a limit of the arch.

Also, look at your JVM heap size.