RFR: Defer cleaning of system dictionary and friends to parallel cleaning phase

[Aleksey Shipilev]

On 01/16/2018 08:48 PM, Zhengyu Gu wrote:
> 
> 
> On 01/16/2018 01:15 PM, Roman Kennke wrote:
>> Am 16.01.2018 um 19:09 schrieb Aleksey Shipilev:
>>> On 01/16/2018 06:59 PM, Roman Kennke wrote:
>>>> Found this during traversal GC work: when cleaning the system dictionary and friends, we do
>>>> clean it
>>>> in the first pass, *single threaded* and then do the cleaning stuff again, but multi-threaded. We
>>>> shall defer cleaning to the parallel phase to begin with. That's what G1 does too.
>>>>
>>>> http://cr.openjdk.java.net/~rkennke/defer_cleaning/webrev.00/
>>>>
>>>
>>> Awwwwwwww.
>>>
>>> Note that in G1, there are two calls to do_unloading: one from weak_refs_work with "false", and
>>> another from mark_sweep_phase1 with default "true".
>>
>> For ordinary concurrent GCs, it cleans everything in parallel phase, and thus passes 'false' to
>> do_unloading(). For full-GC, I guess they don't care and do everything single-threaded.
>>
>>> Are you saying that doing this once with "false" is enough? It looks that ParallelCleaning stuff
>>> purges ResolvedMethodTable, but does it do ClassLoaderDataGraph::do_unloading with
>>> clean_previous_versions? Maybe we should cautiously say "full_gc", not "false" in the patch, so
>>> last-ditch can still do it?
>>
>> I believe the ParallelCleaning handles everything. Zhengyu?
> ParallelCleaning does handle ResolvedMethodTable ...

Ok then!

-Aleksey