Bisection points to JDK-8211400 as the point where it started, but that is likely a trigger.

$ CONF=linux-aarch64-server-fastdebug make images test TEST=vmTestbase/gc/gctests/MemoryEaterMT/MemoryEaterMT.java TEST_VM_OPTS="-XX:+UseShenandoahGC"

...

ava.lang.RuntimeException: java.lang.NoClassDefFoundError: Could not initialize class jdk.test.lib.Utils
        at nsk.share.gc.gp.GarbageUtils.eatMemory(GarbageUtils.java:265)
        at nsk.share.gc.gp.GarbageUtils.eatMemory(GarbageUtils.java:196)
        at nsk.share.gc.Algorithms.eatMemory(Algorithms.java:91)
        at gc.gctests.MemoryEaterMT.MemoryEaterMT$Eater.run(MemoryEaterMT.java:48)
        at nsk.share.runner.ThreadsRunner$ManagedThread.run(ThreadsRunner.java:119)
        at java.base/java.lang.Thread.run(Thread.java:1516)
Caused by: java.lang.NoClassDefFoundError: Could not initialize class jdk.test.lib.Utils
        at nsk.share.test.LocalRandom$1.initialValue(LocalRandom.java:44)
        at nsk.share.test.LocalRandom$1.initialValue(LocalRandom.java:39)
        at java.base/java.lang.ThreadLocal.setInitialValue(ThreadLocal.java:203)
        at java.base/java.lang.ThreadLocal.get(ThreadLocal.java:193)
        at java.base/java.lang.ThreadLocal.get(ThreadLocal.java:171)
        at nsk.share.test.LocalRandom.nextInt(LocalRandom.java:288)
        at nsk.share.test.LocalRandom.nextInt(LocalRandom.java:303)
        at nsk.share.test.LocalRandom.nextByte(LocalRandom.java:74)
        at nsk.share.test.LocalRandom.nextBytes(LocalRandom.java:97)
        at nsk.share.gc.gp.array.ByteArrayProducer.create(ByteArrayProducer.java:37)
        at nsk.share.gc.gp.array.ByteArrayProducer.create(ByteArrayProducer.java:34)
        at nsk.share.gc.gp.GarbageUtils.eatMemoryImpl(GarbageUtils.java:302)
        at nsk.share.gc.gp.GarbageUtils.eatMemory(GarbageUtils.java:258)
        ... 5 more
Caused by: java.lang.ExceptionInInitializerError: Exception java.lang.OutOfMemoryError: Java heap space [in thread "gc.gctests.MemoryEaterMT.MemoryEaterMT$Eater@1d5e6100"]