On 07/23/2013 10:19 AM, David Holmes wrote: > Hi Jaroslav, > > On 22/07/2013 9:55 PM, Jaroslav Bachorik wrote: >> The java/lang/management/ThreadMXBean/ResetPeakThreadCount.java test >> seems to be failing intermittently. >> >> The test checks the functionality of the >> j.l.m.ThreadMXBean.resetPeakThreadCount() method. It does so by >> capturing the current value of "getPeakThreadCount()", starting a >> predefined number of the user threads, stopping them and resetting the >> stored peak value and making sure the new peak equals to the number of >> the actually running threads. >> >> The main problem is that it is not possible to prevent JVM to start/stop >> arbitrary system threads while executing the test. This might lead to >> small variations of the reported peak (a short-lived system thread is >> started while the batch of the user threads is running) or the expected >> number of running threads (again, a short-lived system thread is started >> at the moment the test asks for the number of running threads). > > Do you know what "system threads" these are? I would not expect VM > internal threads to be counted in getPeakThreadCount(), but even if they > are I can't think of any short-lived threads that get created other than > the Signal handling thread.
Unfortunatelly I don't. Capturing the thread dump at the moment of discovering the discrepancy seems to to be too late. I tried monitoring the JVM under the test from external tools but it just brings more entropy to the result. I am completely relying on the JVM native thread accounting to be correct and accurate - that it reports the thread count peak based on the real data. -JB- > >> The patch does not fix those shortcomings as it is not really possible >> to do given the nature of the JVM threading system. It rather tries to >> relax the conditions while still maintaining the ability to detect >> functional problems - eg. decreasing peak without explicitly resetting >> it and reporting false number of threads. >> >> The webrev is at: >> http://cr.openjdk.java.net/~jbachorik/8020875/webrev.00 > > Seems reasonable. > > David > ----- > >> Thanks, >> >> -JB- >>
