On 27.11.2006 08:17, Daniel Pitts wrote:
Patricia Shanahan wrote:
I would like to collect, inside a Java application, statistics such as
the amount of CPU time used. Any idea how?
I can, of course, measure the elapsed time, but that does not tell me
how much time was spent actually computing vs. waiting for disk.
Patricia
A quick googling leads me to believe you might need to use JNI (and
therefore have a platform-specific solution)
<http://www.google.com/search?q=java+system+monitoring>
Example for CPU on Win32
<http://www.javaworld.com/javaworld/javaqa/2002-11/01-qa-1108-cpu.html>
JVMTI might also help:
http://java.sun.com/j2se/1.5.0/docs/guide/jvmti/index.html
http://java.sun.com/j2se/1.5.0/docs/guide/jvmti/jvmti.html#timers
A low level solution would be to create a TimedInputStream and
TimedOutputStream which measure and sum up time spend in write() and
read(). You could then substract that from wall clock for this
thread. If you want to get more fancy those streams could register
themselves with some thread global counter so you automatically get
all IO timings if you make sure every stream is replaced (not easy
though with 3rd party libs like JDBC drivers). It depends on what you
actually want to measure and to what level of detail.
JVMTI looks interesting. The disk accesses that I'm worried about are