JDK-8252802: java launcher should set MALLOCOPTIONS and LDR_CNTRL in order to use 64KB pages on AIX

[varada1110]

DeCapo Benchmark Results (3 runs) :

Before :
===== DaCapo 9.12 h2 PASSED in 281402 msec =====
===== DaCapo 9.12 h2 PASSED in 269818 msec =====
===== DaCapo 9.12 h2 PASSED in 279279 msec =====

After:
===== DaCapo 9.12 h2 PASSED in 279192 msec =====
===== DaCapo 9.12 h2 PASSED in 269769 msec =====
===== DaCapo 9.12 h2 PASSED in 271577 msec =====

Environmental variables LDR_CNTRL and MALLOCOPTIONS has caused test/jdk/java/lang/ProcessBuilder/Basic.java failure.
Additional environmental variables has to removed from removeAixExpectedVars().

JBS Issue : JDK-8252802

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Issue

• JDK-8252802: java launcher should set MALLOCOPTIONS and LDR_CNTRL in order to use 64KB pages on AIX (Enhancement - P4)

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[bridgekeeper]

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[openjdk]

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[mlbridge]

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• 00: Full (035700bf)

[AlanBateman]

Question: Is the java launcher the right place for this? I'm wondering about other launchers that uses JNI Invocation API to create the VM.

[dholmes-ora]

I concur with Alan: is this the right way to fix this? And is it really the case that every single Java application on AIX wants this setting?

[tstuefe]

I don't think this works as intended.

IIRC, both variables must be set before process invocation. Setting them inside the launcher will only affect child processes. The dacapo results posted seem to support this, they seem random-ish to me.

Note that we already use 64KB pages for all large memory regions (everything that goes through os::reserve_memory). So, while the value of LDRCNTRL is not nil, it is very diminished. Mostly just the C-Heap would be affected.

But I would not change defaults for options like these anyway, especially not hard-coded. These knobs have far-ranging implications. If we want that, we need to investigate carefully.

(for example: would using 64KB pages increase average heap size? Possibly, depending on the implementation. But AIX still has this problem where the heap can only live in the break and can bump against low-hanging regions. So, AIX is especially vulnerable against any changes that increase average heap usage)

[varada1110]

Thanks @tstuefe for the response. Closing the PR since it is not advisable to do.