RFR: 8253064: monitor list simplifications and getting rid of TSM [v6]

[Daniel D.Daugherty]

On Wed, 11 Nov 2020 13:50:08 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> src/hotspot/share/runtime/synchronizer.cpp line 246:
>> 
>>> 244: //
>>> 245: // Start the ceiling with the estimate for one thread:
>>> 246: jint _in_use_list_ceiling = AvgMonitorsPerThreadEstimate;
>> 
>> Why is this a jint when you use size_t for its accessor and all the other sizes that you compare with the ceiling are also size_t?
>> I'm not sure size_t is right to use in these cases (do we really expect different maximums on 32-bit versus 64-bit?) but it should be all or none IMO.
>
> Our int types are really confused.  AvgMonitorsPerThreadEstimate is defined as an intx which is intptr_t and the range of it is 0..max_jint which is 0 .. 0x7fffffff . jint is long on windows (the problematic type) and int on unix.  Since this is a new declaration, it probably should be something other than jint but what?
> At any rate, it should be declared as 'static'.

`_in_use_list_ceiling` is a jint **because** we've specified the range
as `0..max_jint` and I wanted some sanity to that variable's type.

If I change `_in_use_list_ceiling` to `size_t`, then I get a compile time
error probably because  `AvgMonitorsPerThreadEstimate` is an `intx`
which (I think) is my only choice for a command line option.

@fisk will have to chime in with the background on why he picked `size_t`.

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PR: https://git.openjdk.java.net/jdk/pull/642