The current way serviceability/sa/TestJmapCore.java runs the Java process that produces the core file doesn't specify a maximum heap size. On Twitter's internal testing infrastructure this can lead to 8GB core files and 4GB hprof files. The test then times out trying to parse the hprof file:

"SameVMThread" #27 prio=5 os_prio=0 cpu=858571.46ms elapsed=960.30s tid=0x00007f800c6fd800 nid=0xb55d runnable [0x00007f7f91888000]
   java.lang.Thread.State: RUNNABLE
at java.io.RandomAccessFile.read0(java.base@11-internal/Native Method)
at java.io.RandomAccessFile.read(java.base@11-internal/RandomAccessFile.java:366)
at java.io.RandomAccessFile.readInt(java.base@11-internal/RandomAccessFile.java:835)
at java.io.RandomAccessFile.readLong(java.base@11-internal/RandomAccessFile.java:870)
at jdk.test.lib.hprof.parser.FileReadBuffer.getLong(FileReadBuffer.java:87)
- locked <0x00000000fc4d3ee8> (a jdk.test.lib.hprof.parser.FileReadBuffer)
at jdk.test.lib.hprof.model.JavaLazyReadObject.longAt(JavaLazyReadObject.java:156)
at jdk.test.lib.hprof.model.JavaLazyReadObject.objectIdAt(JavaLazyReadObject.java:130)
at jdk.test.lib.hprof.model.JavaObjectArray.readValue(JavaObjectArray.java:159)
at jdk.test.lib.hprof.model.JavaLazyReadObject.getValue(JavaLazyReadObject.java:81)
at jdk.test.lib.hprof.model.JavaObjectArray.getElements(JavaObjectArray.java:90)
at jdk.test.lib.hprof.model.JavaObjectArray.visitReferencedObjects(JavaObjectArray.java:106)
at jdk.test.lib.hprof.model.Snapshot.calculateReferencesToObjects(Snapshot.java:323)
at jdk.test.lib.hprof.model.Snapshot.resolve(Snapshot.java:291)
at jdk.test.lib.hprof.HprofParser.parse(HprofParser.java:87)
at jdk.test.lib.hprof.HprofParser.parse(HprofParser.java:54)
at TestJmapCore.test(TestJmapCore.java:140)
at TestJmapCore.main(TestJmapCore.java:71)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(java.base@11-internal/Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(java.base@11-internal/NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(java.base@11-internal/DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(java.base@11-internal/Method.java:566)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:229)
at java.lang.Thread.run(java.base@11-internal/Thread.java:834)