Fwd: RFR: 8175917: [JVMCI] Avoid long JNI handle chains

[Christian Haeubl]

Only Tom Rodriguez (never)

- Christian


Am 02.03.2017 um 17:06 schrieb Vladimir Kozlov:
> Looks good. Who with OpenJDK id reviewed it in Labs? I need to list 
> them in changeset.
>
> Thanks,
> Vladimir
>
> On 3/2/17 7:47 AM, Christian Haeubl wrote:
>> Hi,
>>
>> Please review the following patch for
>> https://bugs.openjdk.java.net/browse/JDK-8175917:
>> http://cr.openjdk.java.net/~never/8175917/webrev.001/
>>
>> Bug description:
>> When Truffle uses JMVCI and Graal for compiling a guest language (e.g.
>> JavaScript), Graal heavily uses partial escape analysis. In such cases,
>> the JVMCI method "installCode" uses lots of local JNI references when
>> generating the corresponding debug information so that the thread's
>> top-level JNI handle buffer will have a large size. This unnecessarily
>> increases the footprint and significantly decreases the performance (as
>> long as https://bugs.openjdk.java.net/browse/JDK-8175318 is not fixed).
>>
>> Fix:
>> Around the JVMCI method "installCode", we do something similar to JNI's
>> PushLocalFrame/PopLocalFrame. So, the large JNI handle buffer is
>> released when the method exits and the thread's top-level JNI handle
>> buffer is not getting enlarged.
>>
>> Tests:
>> The changes were tested locally by executing JVMCI bootstrapping and
>> parts of Graal / Truffle.
>>
>> Thanks,
>> Christian