Hi Mandy,
Mandy Chung said the following on 09/03/09 05:25:
This is related to 6857194: Add hotspot new perf counters to aid class
loading performance measurement.
It's useful to add performance counters in the library code so that perf
data from the JDK and VM can be collected and output in a unified way
(written in the jvmstat shared memory buffer). I add a simple
sun.misc.PerfCounter class to maintain the list of perf counters for the
library to use. This fix only instruments the class loading and jar/zip
to collect simple basic metrics. Additional perf counters will be
added in the future.
Webrev:
http://cr.openjdk.java.net/~mchung/6878481/webrev.00/
What is the performance overhead here? This seems like a lot of extra
code if you don't want to read the counters. Is there not some way to
only conditionally enable them?
We're sticking in a lot of System.nanoTime() calls and on some systems
it isn't necessarily cheap eg Windows - see 6440250. Even if it is
cheap, there are potentially a lot of them in classloading intensive
situations.
David
