public void populateDataPutOnSameKey() {
    // Put for validation.
    putForValidation(region);
    final byte[] value = new byte[ENTRY_SIZE];
    Arrays.fill(value, (byte) 77);
    long startTime = System.currentTimeMillis();
    for (int i = 0; i < OP_COUNT; i++) {
      region.put("K", value);
    }
    long endTime = System.currentTimeMillis();
    System.out.println(" done with putting");
    // validate put operation
    validatePut(region);
    region.close(); // closes disk file which will flush all buffers
    float et = endTime - startTime;
    float etSecs = et / 1000f;
    float opPerSec = etSecs == 0 ? 0 : (OP_COUNT / (et / 1000f));
    float bytesPerSec = etSecs == 0 ? 0 : ((OP_COUNT * ENTRY_SIZE) / (et / 1000f));
    stats_ForSameKeyputs = "et=" + et + "ms writes/sec=" + opPerSec + " bytes/sec=" + bytesPerSec;
    log = ds.getLogWriter();
    log.info(stats_ForSameKeyputs);
  }
OP_COUNT can be increased/decrease as per the requirement. If required to be set as higher
value such as 1000000 one needs to set the VM heap size accordingly. (For example:Default
setting in build.xml is <jvmarg value="-Xmx256M"/>
geode-core/src/performanceTest/java/org/apache/geode/internal/cache/diskPerf/DiskRegionPerfJUnitPerformanceTest.java