RFR: 8292082: Deprecate UseRTM* for removal

[Sandhya Viswanathan]

On Fri, 12 Aug 2022 20:21:12 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> Good.
>> 
>> @sviswa7 do you agree with deprecating this feature?
>
>> @vnkozlov @rkennke RTM feature is available on Intel ICX as well as upcoming Xeon platforms.
> 
> Ok, interesting. I did not know that.
> Is our RTM locking implementation still useful, though? Does it have advantages over locking without RTM, and if so, what are they?

@rkennke RTM locking provides benefit of fine grain lock performance with coarse grain lock. It is useful when there is high contention on lock and low conflict in the critical region.

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PR: https://git.openjdk.org/jdk/pull/9810