meminfo: Add meminfo corelens module

[jianfenw]

This commit implements a meminfo corelens module that enables users to dump detailed statistics of the memory management subsystem. The output is similar to 'cat /proc/meminfo', which includes many aspects of the mm subsystem.

This module supports UEK 5, 6, and 7 and for both x86-64 and aarch64. It is tested for all these above settings. For each case, this meminfo module's output is compared against the output of cat /proc/meminfo. Results match closely with only small differences.

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[brenns10]

Hey @jianfenw , please double check the internal docs regarding Github profiles. I see that the "oracle-samples" organization membership is public. Did you make sure to add your Oracle email address to your account?

[jianfenw]

Thanks, Stephen. The OCA check failed because I didn't make my membership in oracle public when I submitted this PR. I made my memberships in oracle and oracle-samples public afterwards. However, the OCA check didn't get updated automatically. I may have to update the commit to trigger a new check later.

[brenns10]

This is a pretty excellent job! You managed to fit a lot of logic into this. Most of my review comments have to do with the use of global variables, but the logic itself seems sound.

[jianfenw]

I've resolved comments and also included uek4 support. This branch has passed all CI tests.
Please review again. Thank you.

[brenns10]

This is looking good, but still needs some work around caching. This needs to work correctly on live systems, and give always up-to-date statistics each time you run it. That means you need to limit the use of caching. I've provided several suggestions inline.

[jianfenw]

Thank you Stephen. I have updated the commit according to your comments. Appreciate all your wonderful suggestions.

[brenns10]

I have just three little nits here, overall this is good. The most difficult one here is with respect to VMALLOC_END on aarch64, and I'd honestly suggest you just omit the vmalloc info on aarch64, and omit the vmalloc statistic when you go to print everything out.

I checked the internal CI and the failures all have to do with the currently quite flaky in-flight I/O test. I may need to disable that test or find some way to make it a bit better. In any case, all the vmcores passed.

Overall it's looking good and I expect to merge it after these quick changes. Thank you!

[jianfenw]

Updated this commit accordingly! Thank you, Stephen.

[brenns10]

Thanks for iterating on this, it looks great! I checked the tests, and the only failures on the vmcores were the ones on the in-flight I/O test, which are fixed in #28. So it's good to merge!