8358748: Large page size initialization fails with assert "page_size must be a power of 2"

[nelanbu]

The VM now exits gracefully if -XX:LargePageSizeInBytes is set to a non power of two value, instead of asserting. After this change, SizeTTest.java failed because the tested values are not valid for -XX:LargePageSizeInBytes (LargePageSizeInBytesConstraintFunc returns JVMFlag::VIOLATES_CONSTRAINT). Therefore, I updated the test to use NUMASpaceResizeRate, since I believe that it only requires a flag of type size_t.

Before the change:

java -XX:+UseLargePages -XX:LargePageSizeInBytes=6 -version

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (workspace/open/src/hotspot/share/runtime/os.cpp:2449), pid=1885945, tid=1885946
# assert(is_power_of_2(page_size)) failed: page_size must be a power of 2: 0x6

After the change:

java -XX:+UseLargePages -XX:LargePageSizeInBytes=6 -version

LargePageSizeInBytes ( 6 ) must be a power of 2
Improperly specified VM option 'LargePageSizeInBytes=6'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

---

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Issue

• JDK-8358748: Large page size initialization fails with assert "page_size must be a power of 2" (Bug - P4)

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• 01: Full - Incremental (f16b9a57)
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[dholmes-ora]

The -XX:LargePageSizeInBytes flag seems poorly specified. You can't use an arbitrary value in bytes as a large page size - that is just non-sensical. But I'm not sure this should be a hard error rather than applying "ergonomics" and rounding the supplied value to the nearest power-of-2 (with a warning this has happened).