How to monitor free memory ( including buffers and cache) in java?

Question

I've already searched for possible solutions, such as How to monitor the computer's cpu, memory, and disk usage in Java?. But memory spent in buffers and cache is not mentioned anywhere?

For example, on linux, output of free -m:

             total       used       free     shared    buffers     cached
Mem:          2011       1835        175          0        309        847
-/+ buffers/cache:        678       1333
Swap:         1998          0       1998

I've already tested output of sigar, which reports free memory as 175 MB.

The cause of this question is how to detect when OS has little memory left? In the previous output of free -m, 175 MB seems quite low; but by adding buffers and cache it is evident that free memory is actually 1333 MB out of 2 GB.

To summarise, using java, is it possible to get value 1333 MB as value of the free memory? As I've already mentioned, so far I know only how to get value of 175 MB.

Answer 1

If you are trying to get memory statistics for the OS itself (not the JVM), you can use JNA or JNI to make the platform-specific native API calls directly to the OS.

Answer 2

I don't know about free memory directly, but the JVM maintains JMX beans that, I believe, have this information and more: http://docs.oracle.com/javase/1.5.0/docs/guide/management/jconsole.html

Answer 3

I am convinced it is not possible to use Java API for obtaining cahce/buffers number. Even the guys from SIGAR use JNI wrappers and native system calls...