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