RFR: 8250984: Memory Docker tests fail on some Linux kernels w/o cgroupv1 …

[Severin Gehwolf]

On Fri, 25 Sep 2020 14:12:02 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

>> test/hotspot/jtreg/containers/docker/TestMemoryAwareness.java line 163:
>> 
>>> 161:         // or the cgroup is not mounted. Memory limited without swap."
>>> 162:         // the getTotalSwapSpaceSize does not return the expected result and
>>> 163:         // getFreeSwapSpaceSize returns 0
>> 
>> https://bugs.openjdk.java.net/browse/JDK-8244500 indicates a system where we have the kernel warning, but
>> getFreeSwapSpaceSize() returned the system values. *Not* 0 as indicated in this comment. This yields me to believe
>> there are inconsistently behaving systems out there. Could we rephrase this comment?
>
> Thanks for reviewing this!
> Does this change to the comment look better?
> 
> `          // in case of warnings like : "Your kernel does not support swap limit capabilities
>            // or the cgroup is not mounted. Memory limited without swap."
>           // the getTotalSwapSpaceSize and getFreeSwapSpaceSize return the system
>           // values as the container setup isn't supported in that case.
> `

This looks fine. Thanks!

>> test/hotspot/jtreg/containers/docker/TestMemoryAwareness.java line 167:
>> 
>>> 165:             out.shouldContain("OperatingSystemMXBean.getTotalSwapSpaceSize: " + expectedSwap);
>>> 166:         } catch(RuntimeException ex) {
>>> 167:             out.shouldMatch("OperatingSystemMXBean.getTotalSwapSpaceSize: -?([0-9]+)");
>> 
>> Is the optional `-` intentional? My understanding is that it should never be negative, should it not?
>
> The optional - is intential in case UNLIMITED is return (-1).

Hmm, but the OperatingSystemMXBean impl falls back to returning the system (host) values if the container limits are
unlimited. So the internal Metrics value of -1 for UNLIMITED should never be seen. Has this been actually seen in some
tests somewhere?

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PR: https://git.openjdk.java.net/jdk/pull/342