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

[Baesken, Matthias]

Hi  David,   thanks for  the info about 

https://bugs.openjdk.java.net/browse/JDK-8228990


regarding your comment in the bug :

> So it makes no sense. I finally found an example where the test passed and failed on the same machine.

I've seen this too .

Looks like  my change  only  increased  the probability of  incidental network traffic happening  on the real network interfaces .

Should we exclude the test,  in the current state it might indeed be problematic .

(otherwise we could make the test pass  on Linux  when just 1 network interface is found,  this might be a legitimate case isn’t it ?)


Best regards, Matthias



> -----Original Message-----
> From: David Holmes <david.holmes at oracle.com>
> Sent: Dienstag, 27. August 2019 09:56
> To: Baesken, Matthias <matthias.baesken at sap.com>; 'hotspot-
> dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>; hotspot-jfr-
> dev at openjdk.java.net
> Subject: Re: RFR [XS]: 8229370: make
> jdk/jfr/event/runtime/TestNetworkUtilizationEvent.java more stable
> 
> Hi Matthias,
> 
> On 27/08/2019 5:41 pm, Baesken, Matthias wrote:
> > Hello, any reviews for this small change ?
> 
> I missed the initial request - sorry.
> 
> Seems we have a double up of effort here as we also have JDK-8228990 for
> the exact same problem that we see on some of our test machines.
> 
> Our analysis suggests that this test often passes by accident due to
> incidental activity on the real network interface when the logic
> intended to generate that activity (the packet sent to 10.0.0.0:12345)
> actually had no affect (unreachable address). If there is no incidental
> network activity then the real network interface is not seen and so the
> test fails.
> 
> David
> 
> > Thanks , Matthias
> >
> > From: Baesken, Matthias
> > Sent: Montag, 12. August 2019 14:33
> > To: 'hotspot-dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>;
> 'hotspot-jfr-dev at openjdk.java.net' <hotspot-jfr-dev at openjdk.java.net>
> > Subject: RFR [XS]: 8229370: make
> jdk/jfr/event/runtime/TestNetworkUtilizationEvent.java more stable
> >
> > 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
> >