RFR(L) 8227745: Enable Escape Analysis for Better Performance in the Presence of JVMTI Agents

[Vladimir Kozlov]

Hi David,

Tiered is disabled because we don't want to see compilations and outputs 
from C1 compiler which does not have EA.

The test is specifically written for C2 only (not for C1 or Graal) to 
verify its Escape Analysis optimization.
I did not look in great details into test's code but its analysis may be 
affected if C1 compiler is also used.

Richard may clarify this.

thanks,
Vladimir

On 12/11/19 1:04 PM, David Holmes wrote:
> On 12/12/2019 5:21 am, Vladimir Kozlov wrote:
>> I will do full review later. I want to comment about test command line.
>>
>> You don't need vm.opt.TieredCompilation != true in @requires because 
>> you specified -XX:-TieredCompilation in @run command.
> 
> And per my comment this should be being tested with tiered as well.
> 
> David
> 
>> Use vm.compMode == "Xmixed" instead of vm.compMode != "Xcomp" to skip 
>> test from running in Interpreter mode too.
>>
>> Thanks,
>> Vladimir
>>
>> On 12/11/19 7:07 AM, Reingruber, Richard wrote:
>>> Hi David,
>>>
>>>    > Most of the details here are in areas I can comment on in 
>>> detail, but I
>>>    > did take an initial general look at things.
>>>
>>> Thanks for taking the time!
>>>
>>>    > The only thing that jumped out at me is that I think the
>>>    > DeoptimizeObjectsALotThread should be a hidden thread.
>>>    >
>>>    > +  bool is_hidden_from_external_view() const { return true; }
>>>
>>> Yes, it should. Will add the method like above.
>>>
>>>    > Also I don't see any testing of the DeoptimizeObjectsALotThread. 
>>> Without
>>>    > active testing this will just bit-rot.
>>>
>>> DeoptimizeObjectsALot is meant for stress testing with a larger 
>>> workload. I will add a minimal test
>>> to keep it fresh.
>>>
>>>    > Also on the tests I don't understand your @requires clause:
>>>    >
>>>    >   @requires ((vm.compMode != "Xcomp") & vm.compiler2.enabled &
>>>    > (vm.opt.TieredCompilation != true))
>>>    >
>>>    > This seems to require that TieredCompilation is disabled, but 
>>> tiered is
>>>    > our normal mode of operation. ??
>>>    >
>>>
>>> I removed the clause. I guess I wanted to target the tests towards 
>>> the code they are supposed to
>>> test, and it's easier to analyze failures w/o tiered compilation and 
>>> with just one compiler thread.
>>>
>>> Additionally I will make use of 
>>> compiler.whitebox.CompilerWhiteBoxTest.THRESHOLD in the tests.
>>>
>>> Thanks,
>>> Richard.
>>>
>>> -----Original Message-----
>>> From: David Holmes <david.holmes at oracle.com>
>>> Sent: Mittwoch, 11. Dezember 2019 08:03
>>> To: Reingruber, Richard <richard.reingruber at sap.com>; 
>>> serviceability-dev at openjdk.java.net; 
>>> hotspot-compiler-dev at openjdk.java.net; 
>>> hotspot-runtime-dev at openjdk.java.net
>>> Subject: Re: RFR(L) 8227745: Enable Escape Analysis for Better 
>>> Performance in the Presence of JVMTI Agents
>>>
>>> Hi Richard,
>>>
>>> On 11/12/2019 7:45 am, Reingruber, Richard wrote:
>>>> Hi,
>>>>
>>>> I would like to get reviews please for
>>>>
>>>> http://cr.openjdk.java.net/~rrich/webrevs/2019/8227745/webrev.3/
>>>>
>>>> Corresponding RFE:
>>>> https://bugs.openjdk.java.net/browse/JDK-8227745
>>>>
>>>> Fixes also https://bugs.openjdk.java.net/browse/JDK-8233915
>>>> And potentially https://bugs.openjdk.java.net/browse/JDK-8214584 [1]
>>>>
>>>> Vladimir Kozlov kindly put webrev.3 through tier1-8 testing without 
>>>> issues (thanks!). In addition the
>>>> change is being tested at SAP since I posted the first RFR some 
>>>> months ago.
>>>>
>>>> The intention of this enhancement is to benefit performance wise 
>>>> from escape analysis even if JVMTI
>>>> agents request capabilities that allow them to access local variable 
>>>> values. E.g. if you start-up
>>>> with -agentlib:jdwp=transport=dt_socket,server=y,suspend=n, then 
>>>> escape analysis is disabled right
>>>> from the beginning, well before a debugger attaches -- if ever one 
>>>> should do so. With the
>>>> enhancement, escape analysis will remain enabled until and after a 
>>>> debugger attaches. EA based
>>>> optimizations are reverted just before an agent acquires the 
>>>> reference to an object. In the JBS item
>>>> you'll find more details.
>>>
>>> Most of the details here are in areas I can comment on in detail, but I
>>> did take an initial general look at things.
>>>
>>> The only thing that jumped out at me is that I think the
>>> DeoptimizeObjectsALotThread should be a hidden thread.
>>>
>>> +  bool is_hidden_from_external_view() const { return true; }
>>>
>>> Also I don't see any testing of the DeoptimizeObjectsALotThread. Without
>>> active testing this will just bit-rot.
>>>
>>> Also on the tests I don't understand your @requires clause:
>>>
>>>    @requires ((vm.compMode != "Xcomp") & vm.compiler2.enabled &
>>> (vm.opt.TieredCompilation != true))
>>>
>>> This seems to require that TieredCompilation is disabled, but tiered is
>>> our normal mode of operation. ??
>>>
>>> Thanks,
>>> David
>>>
>>>> Thanks,
>>>> Richard.
>>>>
>>>> [1] Experimental fix for JDK-8214584 based on JDK-8227745
>>>> http://cr.openjdk.java.net/~rrich/webrevs/2019/8214584/experiment_v1.patch 
>>>>
>>>>