RFR [XS]: 8229370: make jdk/jfr/event/runtime/TestNetworkUtilizationEvent.java more stable

Mon Aug 12 12:32:42 UTC 2019

Hello, please review this small test enhancement.

We noticed that on some of our Linux machines  (SLES12 based)   the TestNetworkUtilizationEvent.java test reported just 1 interface
(the test  TestNetworkUtilizationEvent.java  expects more than 1 on Linux).

Looking into the HS code , os_perf_linux.cpp collects the interfaces + additional information about bytes read/written  (by looking at  /sys/class/net/eth<X>/statistics/<countername>  )
and this info is given to JFR .

However it seems to need (at least on some machines / setups) more packet send operations / potential  retries to really  get counter updates   (and without updates in the counters,   no interfaces are found).
So I adjusted the test accordingly.

Bug/webrev :

https://bugs.openjdk.java.net/browse/JDK-8229370

http://cr.openjdk.java.net/~mbaesken/webrevs/8229370.0/

Best regards, Matthias