RFR: JDK-8256725: Metaspace: better blocktree and binlist asserts [v3]

[Thomas Stuefe]

On Mon, 23 Nov 2020 10:39:06 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Quick node checks in blocktree on insert/removal
>
> Looks good. I like the canary in Node. I have three minor comments you should take a look at.

Richard, Leo,

thanks for reviewing!

I fixed your remarks. Changes in the last commit:
- %d -> %u
- split multiline assert into two asserts
- simplified NODE_FORMAT_ARGS
- When verifying a tree, I have now special handling for unreadable node pointers and node pointers whose canaries are invalid. In the former case I assert right away, in the latter I print the node as hex dump (I considered doing further analysis like "is in metaspace" which would be trivial but this class is earmarked as a potential future generic class so I did not want to add deps to metaspace).
- When an error is detected, the whole tree is printed; now tree printing tippytoes around invalid pointers.

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PR: https://git.openjdk.java.net/jdk/pull/1339