test/jdk/jdk/jfr/event/compiler/TestAllocInNewTLAB.java

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package jdk.jfr.event.compiler;

import static java.lang.Math.floor;
import static jdk.test.lib.Asserts.assertGreaterThanOrEqual;
import static jdk.test.lib.Asserts.assertLessThanOrEqual;

import java.time.Duration;

import jdk.jfr.Recording;
import jdk.jfr.consumer.RecordedEvent;
import jdk.test.lib.jfr.EventNames;
import jdk.test.lib.jfr.Events;

/*
 * @test
 * @summary Test that event is triggered when an object is allocated in a new TLAB.
 * @key jfr
 * @library /test/lib
 * @run main/othervm -XX:+UseTLAB -XX:TLABSize=100k -XX:-ResizeTLAB -XX:TLABRefillWasteFraction=1 jdk.jfr.event.compiler.TestAllocInNewTLAB
 * @run main/othervm -XX:+UseTLAB -XX:TLABSize=100k -XX:-ResizeTLAB -XX:TLABRefillWasteFraction=1 -XX:-FastTLABRefill jdk.jfr.event.compiler.TestAllocInNewTLAB
 * @run main/othervm -XX:+UseTLAB -XX:TLABSize=100k -XX:-ResizeTLAB -XX:TLABRefillWasteFraction=1 -Xint jdk.jfr.event.compiler.TestAllocInNewTLAB
 */

/**
 * Test that when an object is allocated in a new Thread Local Allocation Buffer (TLAB)
 * an event will be triggered. The test is done for C1-compiler,
 * C2-compiler (-XX:-FastTLABRefill) and interpreted mode (-Xint).
 *
 * To force objects to be allocated in a new TLAB:
 *      the size of TLAB is set to 100k (-XX:TLABSize=100k);
 *      the size of allocated objects is set to 100k minus 16 bytes overhead;
 *      max TLAB waste at refill is set to minimum (-XX:TLABRefillWasteFraction=1),
 *          to provoke a new TLAB creation.
 */
public class TestAllocInNewTLAB {
    private final static String EVENT_NAME = EventNames.ObjectAllocationInNewTLAB;

    private static final int BYTE_ARRAY_OVERHEAD = 16; // Extra bytes used by a byte array.
    private static final int OBJECT_SIZE  = 100 * 1024;
    private static final int OBJECT_SIZE_ALT = OBJECT_SIZE + 8; // Object size in case of disabled CompressedOops
    private static final int OBJECTS_TO_ALLOCATE = 100;
    private static final String BYTE_ARRAY_CLASS_NAME = new byte[0].getClass().getName();
    private static final int INITIAL_TLAB_SIZE = 100 * 1024;

    // make sure allocation isn't dead code eliminated
    public static byte[] tmp;

    public static void main(String[] args) throws Exception {
        Recording recording = new Recording();
        recording.enable(EVENT_NAME).withThreshold(Duration.ofMillis(0));

        recording.start();
        System.gc();
        for (int i = 0; i < OBJECTS_TO_ALLOCATE; ++i) {
            tmp = new byte[OBJECT_SIZE - BYTE_ARRAY_OVERHEAD];
        }
        recording.stop();

        int countAllTlabs = 0;  // Count all matching tlab allocations.
        int countFullTlabs = 0; // Count matching tlab allocations with full tlab size.
        for (RecordedEvent event : Events.fromRecording(recording)) {
            if (!EVENT_NAME.equals(event.getEventType().getName())) {
                continue;
            }
            System.out.println("Event:" + event);

            long allocationSize = Events.assertField(event, "allocationSize").atLeast(1L).getValue();
            long tlabSize = Events.assertField(event, "tlabSize").atLeast(allocationSize).getValue();
            String className = Events.assertField(event, "objectClass.name").notEmpty().getValue();

            boolean isMyEvent = Thread.currentThread().getId() == event.getThread().getJavaThreadId()
                 && className.equals(BYTE_ARRAY_CLASS_NAME)
                 && (allocationSize == OBJECT_SIZE || allocationSize == OBJECT_SIZE_ALT);
            if (isMyEvent) {
                countAllTlabs++;
                if (tlabSize == INITIAL_TLAB_SIZE + OBJECT_SIZE || tlabSize == INITIAL_TLAB_SIZE + OBJECT_SIZE_ALT) {
                    countFullTlabs++;
                }
            }
        }

        int minCount = (int) floor(OBJECTS_TO_ALLOCATE * 0.80);
        assertGreaterThanOrEqual(countAllTlabs, minCount, "Too few tlab objects allocated");
        assertLessThanOrEqual(countAllTlabs, OBJECTS_TO_ALLOCATE, "Too many tlab objects allocated");

        // For most GCs we expect the size of each tlab to be
        // INITIAL_TLAB_SIZE + ALLOCATION_SIZE, but that is not always true for G1.
        // G1 may use a smaller tlab size if the full tlab does not fit in the
        // selected memory region.
        //
        // For example, if a G1 memory region has room for 4.7 tlabs,
        // then the first 4 tlabs will have the expected size,
        // but the fifth tlab would only have a size of 0.7*expected.
        //
        // It is only the last tlab in each region that has a smaller size.
        // This means that at least 50% of the allocated tlabs should
        // have the expected size (1 full tlab, and 1 fractional tlab).
        assertGreaterThanOrEqual(2*countFullTlabs, countAllTlabs, "Too many fractional tlabs.");
    }

}