static long calculateRocksDBMutableLimit(long bufferSize) {
        return bufferSize * 7 / 8;
    }
@Test
    public void testCalculateRocksDBMutableLimit() {
        long bufferSize = 64 * 1024 * 1024;
        long limit = bufferSize * 7 / 8;
        assertThat(
                RocksDBMemoryControllerUtils.calculateRocksDBMutableLimit(bufferSize), is(limit));
    }