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package metaspace.gc;

import java.util.Arrays;

import vm.share.VMRuntimeEnvUtils;

/**

 * Test metaspace ergonomic.

 *

 * <ul>

 * <li>MetaspaceSize

 * <li>MaxMetaspaceSize

 * <li>MinMetaspaceFreeRatio

 * <li>MaxMetaspaceFreeRatio

 * </ul>

 *

 * The test loads classes until the committed metaspace achieves the certain

 * level between MetaspaceSize and MaxMetaspaceSize.

 * Then it counts how many times GC has been induced.

 * Test verifies that MinMetaspaceFreeRatio/MaxMetaspaceFreeRatio settings

 * affect the frequency of GC. (High-water mark)

 *

 * Quoting: Java SE 8 HotSpot[tm] Virtual Machine Garbage Collection Tuning

 * <pre>

 * Class metadata is deallocated when the corresponding Java class is unloaded.

 * Java classes are unloaded as a results of garbage collection and garbage

 * collections may be induced in order to unload classes and deallocate class

 * metadata. When the space used for class metadata reaches a certain level

 * (call it a high-water mark), a garbage collection is induced.

 * After the garbage collection the high-water mark may be raised or lowered

 * depending on the amount of space freed from class metadata. The high-water

 * mark would be raised so as not to induce another garbage collection too soon.

 * The high-water mark is initially set to the value of the command-line

 * flag MetaspaceSize . It is raised or lowered based on the flags

 * MaxMetaspaceFreeRatio and MinMetaspaceFreeRatio.

 * If the committed space available for class metadata as a percentage of

 * the total committed space for class metadata is greater than

 * MaxMetaspaceFreeRatio, the high-water mark will be lowered.

 * If it is less than MinMetaspaceFreeRatio, the high-water mark will be raised.

 * </pre>

 */

public class HighWaterMarkTest extends FirstGCTest {

    public static void main(String... args) {

        new HighWaterMarkTest().run(args);

    }

    // value given in -XX:MetaspaceSize=<value>

    private long metaspaceSize = -1;

    // value given in -XX:MaxMetaspaceSize=<value>

    private long maxMetaspaceSize = -1;

    // value given in -XX:MinMetaspaceFreeRatio=<value>

    private long minMetaspaceFreeRatio = -1;

    // value given in -XX:MaxMetaspaceFreeRatio=<value>

    private long maxMetaspaceFreeRatio = -1;

    /**

     * Parses arguments and vm options.

     * Throws Fault in cases of wrong values or missed parameters.

     *

     * @param args command line options

     */

    @Override

    protected void parseArgs(String[] args) {

        if (args.length > 0) {

            printUsage();

            throw new Fault("Illegal arguments: " + Arrays.asList(args));

        }

        if (gclogFileName == null) {

            printUsage();

            throw new Fault("Log file name is not given");

        }

        final String metaSize    = "-XX:MetaspaceSize=";

        final String maxMetaSize = "-XX:MaxMetaspaceSize=";

        final String minRatio    = "-XX:MinMetaspaceFreeRatio=";

        final String maxRatio    = "-XX:MaxMetaspaceFreeRatio=";

        for (String va: vmArgs) {

            if (va.startsWith(metaSize)) {

                metaspaceSize = parseValue(va.substring(metaSize.length()));

            } else if (va.startsWith(maxMetaSize)) {

                maxMetaspaceSize = parseValue(va.substring(maxMetaSize.length()));

            } else if (va.startsWith(minRatio)) {

                minMetaspaceFreeRatio = parseValue(va.substring(minRatio.length()));

            } else if (va.startsWith(maxRatio)) {

                maxMetaspaceFreeRatio = parseValue(va.substring(maxRatio.length()));

            }

        }

        if (metaspaceSize < 0) {

            printUsage();

            throw new Fault("-XX:MetaspaceSize is not specified");

        } else if (maxMetaspaceSize < 0) {

            printUsage();

            throw new Fault("-XX:MaxMetaspaceSize is not specified");

        } else if (minMetaspaceFreeRatio < 0) {

            printUsage();

            throw new Fault("-XX:MinMetaspaceFreeRatio is not specified");

        } else if (maxMetaspaceFreeRatio < 0) {

            printUsage();

            throw new Fault("-XX:MaxMetaspaceFreeRatio is not specified");

        }

    }

    private void printUsage() {

        System.err.println("Usage: ");

        System.err.println("java [-Xlog:gc:<filename>] [-XX:MetaspaceSize=..] [-XX:MaxMetaspaceSize=..] [-XX:MinMetaspaceFreeRatio=..] [-XX:MaxMetaspaceFreeRatio=..] \\");

        System.err.println("    " + HighWaterMarkTest.class.getCanonicalName());

    }

    /**

     * Check that MinMetaspaceFreeRatio/MaxMetaspaceFreeRatio settings

     * affects the moment of the next GC.

     *

     * Eats memory until amount of committed metaspace achieves a certain level

     * (between MetaspaceSize and MaxMetaspaceSize).

     * Then checks how many times GC has been invoked.

     *

     */

    @Override

    public void doCheck() {

        // to avoid timeouts we limit the number of attempts

        int attempts = 0;

        int maxAttempts = 10_000;

        // in between metaspaceSize and maxMetaspaceSize

        // no OOM is exepcted.

        long committedLevel = (metaspaceSize + maxMetaspaceSize) / 2;

        while (getCommitted() < committedLevel && attempts < maxAttempts) {

            attempts++;

            loadNewClasses(9, true);  // load classes and keep references

            loadNewClasses(1, false); // load classes without keeping references

        }

        System.out.println("% Classes loaded: " + attempts*10);

        System.out.println("% Used metaspace    : " + bytes2k(getUsed()));

        System.out.println("% Committed metaspce: " + bytes2k(getCommitted()));

        cleanLoadedClasses();

        if (attempts == maxAttempts) {

            throw new Fault("Committed amount hasn't achieved " + bytes2k(committedLevel));

        }

        int gcCount = getMetaspaceGCCount();

        if (gcCount < 0) {

            // perhpas, it's better to silently pass here... Let's see.

            throw new Fault ("Unable to count full collections, could be an env issue");

        }

        System.out.println("% GC has been invoked: " + gcCount + " times");

        if (maxMetaspaceFreeRatio <= 1) {

            // min/max = 0/1  boundary value

            // GC should happen very often

            checkGCCount(gcCount, 20, -1);

        } else if (minMetaspaceFreeRatio >= 99) {

            // min/max = 99/100  boundary value

            // GC should happen very rare

            checkGCCount(gcCount, -1, 2);

        } else if (minMetaspaceFreeRatio >= 10  && maxMetaspaceFreeRatio <= 20) {

            // GC should happen quite often

            checkGCCount(gcCount, 3, 30);

        } else if (minMetaspaceFreeRatio >= 70  && maxMetaspaceFreeRatio <= 80) {

            // GC should happen quite often

            checkGCCount(gcCount, 1, 3);

        } else {

            // hard to estimate

        }

    }

    /**

     * Checks that count of GC fits the expected range.

     * Throws Fault if count is unexpected.

     *

     * @param count how many times GC has happened

     * @param min   expected minimum, if under zero - undefined

     * @param max   expected maximum, if under zero - undefined

     */

    void checkGCCount(int count, int min, int max) {

        if (min < 0) {

            if(count > max) {

                throw new Fault("GC has happened too often: " + count + " times, " +

                        "expected count: less than " + max);

            }

        } else if (max < 0) {

            if(count < min) {

                throw new Fault("GC has happened too rare: " + count + " times, " +

                        "expected count greater than " + min);

            }

        } else if (count < min || count > max ) {

            throw new Fault ("GC has happened " + count + " times, " +

                    "approximate count is " + min + " to " + max);

        }

    }

}