RFR: 8292170: Convert CodeRootSetTable to use ResourceHashtable [v8]

[Coleen Phillimore]

On Tue, 24 Jan 2023 14:38:49 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> src/hotspot/share/gc/g1/heapRegionRemSet.cpp line 124:
>> 
>>> 122:           BOOL_TO_STR(_m.owned_by_self()), BOOL_TO_STR(Thread::current()->is_VM_thread()));
>>> 123: 
>>> 124:   if (!_code_roots.contains(nm)) { // with this test, we can assert that we do not modify the hash table while iterating over it
>> 
>> But you have the assert in 'add' too, so put_if_absent is more efficient than calling contains first.
>
> When we have an evacuation failure, the code will add an nmethod that is already present. If I guard in `add_code_root_locked`, evacuation failures will not reach the assert in `G1CodeRootSet::add`. Another way to do it is to to do the `contains` within the assert and then somewhat optimising the release build. Would you prefer that?

Oh, I see.  contains() does not have the assert.  Ok, this makes sense.

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PR: https://git.openjdk.org/jdk/pull/11675