RFR: 8262188: Add test to verify trace page sizes logging on Linux

[Stefan Johansson]

On Tue, 23 Feb 2021 21:23:18 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

> Please review this new test that checks the output from `-Xlog:pagesize` and compares it to what's really used according to `/proc/self/smaps`.
> 
> We already have a few tests that check the output from `-Xlog:pagesize`, the difference is that those tests expect some page size given the parameters used. This new test instead check if the values printed out are correct with regards to what is recorded in `/proc/self/maps`.
> 
> I wrote the test to see if all our logging was correct, and found those two issues that are now fixed:
> [JDK-8261029: Code heap page sizes not traced correctly using os::trace_page_sizes](https://bugs.openjdk.java.net/browse/JDK-8261029)
> [JDK-8261230: GC tracing of page sizes are wrong in a few places](https://bugs.openjdk.java.net/browse/JDK-8261230)
> 
> The test now passes and it will be a good way to prevent incorrect page size logging to be added going forward.
> 
> **Testing**
> The new test has been run through mach5 without any problems and also manually on configurations with explicit large pages enabled.

Thanks Thomas for looking at this and highlighting some potential problems. 

I think we should be fine, but I will see if I can trigger a failure caused by any of your concerns :)

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PR: https://git.openjdk.java.net/jdk/pull/2696