RFR 8231264: Disable biased-locking and deprecate all flags related to biased-locking

[David Holmes]

Hi Patricio,

On 16/11/2019 12:15 pm, Patricio Chilano wrote:
> Hi all,
> 
> Could you review the following patch?
> 
> JBS: https://bugs.openjdk.java.net/browse/JDK-8231264
> Webrev: http://cr.openjdk.java.net/~pchilanomate/8231264/v01/webrev
> 
> Biased locking will be disabled by default and all related flags will be 
> deprecated. Performance gains seen when the feature was introduced in 
> the VM are less clear today with modern Java code/processors. Detailed 
> rationale behind the change is included on the description of the bug.

That all seems fine.

> I modified test gtest/oops/test_markWord.cpp so that it still exercises 
> other cases of markword printing.

There seems to be some value in testing things in the non-biased-locking 
case - though I wonder if there is not another gtest that does this?

The only criticism I have is that when BL is disabled the later comments 
in the test are incorrect:

115   // Same thread tries to lock it again.

First time without BL.

121   // This is no longer biased, because ObjectLocker revokes the bias.

Was not biased to begin with without BL.

Thanks,
David

> Tested with mach5, tiers1-6 on all platforms (Linux, macOS, Windows and 
> Solaris).
> 
> Thanks,
> Patricio
> 
>