ADDITIONAL SYSTEM INFORMATION :
Platform:
Windows 10 [Version 10.0.19041.450]
Ryzen 3900x, 32GB RAM

Runtimes:
+ Oracle JDK 1.8
+ OpenJDK 9.0.4
+ OpenJDK 10
+ Zulu 11 / 12 / 13
-  Zulu 14 / 15-EA


A DESCRIPTION OF THE PROBLEM :
This program
-------------------------------------------------
public class uu {
  public static void main(String[] args) throws Throwable {
    long t0 = System.nanoTime();
    Thread.sleep(1);
    System.out.println(System.nanoTime()-t0);
  }
}
-------------------------------------------------

is expected to typically print values of 1ms when run on an otherwise idle system. On Java 13 this was true in >70% of the cases. On Java 14 >80% of the cases report 2ms or higher, and the higher percentiles are noticeably worse.

Percentile chart JDK13: https://ibb.co/Y85DVjC
Percentile chart JDK14: https://ibb.co/jfwj8L4


The below code generates a printout of percentiles
-------------------------------------------------
public class uu {
  public static void main(String[] args) throws Throwable {
    final int n = 10000;

    // sleep for 1ms
    final long[] time = new long[n + 1];
    for (int i = 0; i < time.length; i++) {
        time[i] = System.nanoTime();
        Thread.sleep(1);
    }

    // create sorted time deltas
    final long[] dt = new long[time.length - 1];
    for (int i = 0; i < dt.length; i++) {
        dt[i] = time[i + 1] - time[i];
    }
    Arrays.sort(dt);

    // print percentiles
    final double nsToMs = 1E-6;
    System.out.println(String.format("10    : %.1f ms", dt[(int) (dt.length * 0.100)] * nsToMs));
    System.out.println(String.format("30    : %.1f ms", dt[(int) (dt.length * 0.300)] * nsToMs));
    System.out.println(String.format("50    : %.1f ms", dt[(int) (dt.length * 0.500)] * nsToMs));
    System.out.println(String.format("70    : %.1f ms", dt[(int) (dt.length * 0.700)] * nsToMs));
    System.out.println(String.format("90    : %.1f ms", dt[(int) (dt.length * 0.900)] * nsToMs));
    System.out.println(String.format("95    : %.1f ms", dt[(int) (dt.length * 0.950)] * nsToMs));
    System.out.println(String.format("99    : %.1f ms", dt[(int) (dt.length * 0.990)] * nsToMs));
    System.out.println(String.format("99.9  : %.1f ms", dt[(int) (dt.length * 0.999)] * nsToMs));
    System.out.println(String.format("99.99 : %.1f ms", dt[(int) (dt.length * 0.9999)] * nsToMs));
    System.out.println(String.format("Total runtime: %.1f s", (time[n] - time[0]) * 1E-9));

  }
}
-------------------------------------------------

REGRESSION : Last worked in version 13

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Call Thread.sleep(1) on an idle system and measure the elapsed time (see code example)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
== zulu-13.0.3 ==
10    : 1.0 ms
30    : 1.0 ms
50    : 1.0 ms
70    : 2.0 ms
90    : 2.0 ms
95    : 2.0 ms
99    : 2.2 ms
99.9  : 2.3 ms
99.99 : 3.1 ms
Total runtime: 14.1 s
ACTUAL -
== zulu-14.0.1 ==
10    : 1.0 ms
30    : 2.0 ms
50    : 2.0 ms
70    : 2.8 ms
90    : 3.0 ms
95    : 3.3 ms
99    : 4.0 ms
99.9  : 5.0 ms
99.99 : 6.0 ms
Total runtime: 21.4 s

---------- BEGIN SOURCE ----------
public class uu {
  public static void main(String[] args) throws Throwable {
    final int n = 10000;

    // sleep for 1ms
    final long[] time = new long[n + 1];
    for (int i = 0; i < time.length; i++) {
        time[i] = System.nanoTime();
        Thread.sleep(1);
    }

    // create sorted time deltas
    final long[] dt = new long[time.length - 1];
    for (int i = 0; i < dt.length; i++) {
        dt[i] = time[i + 1] - time[i];
    }
    Arrays.sort(dt);

    // print percentiles
    final double nsToMs = 1E-6;
    System.out.println(String.format("10    : %.1f ms", dt[(int) (dt.length * 0.100)] * nsToMs));
    System.out.println(String.format("30    : %.1f ms", dt[(int) (dt.length * 0.300)] * nsToMs));
    System.out.println(String.format("50    : %.1f ms", dt[(int) (dt.length * 0.500)] * nsToMs));
    System.out.println(String.format("70    : %.1f ms", dt[(int) (dt.length * 0.700)] * nsToMs));
    System.out.println(String.format("90    : %.1f ms", dt[(int) (dt.length * 0.900)] * nsToMs));
    System.out.println(String.format("95    : %.1f ms", dt[(int) (dt.length * 0.950)] * nsToMs));
    System.out.println(String.format("99    : %.1f ms", dt[(int) (dt.length * 0.990)] * nsToMs));
    System.out.println(String.format("99.9  : %.1f ms", dt[(int) (dt.length * 0.999)] * nsToMs));
    System.out.println(String.format("99.99 : %.1f ms", dt[(int) (dt.length * 0.9999)] * nsToMs));
    System.out.println(String.format("Total runtime: %.1f s", (time[n] - time[0]) * 1E-9));

  }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
None. LockSupport::parkNanos on JDK14 fares comparably to JDK13, but there was a regression from Windows build 18362 to 19041 that makes it significantly worse than sleep.

FREQUENCY : always