final long totalBytes = runtime.totalMemory();
        final long usedBytes = totalBytes - freeBytes;
        return "Mem:{used " + byteCountToDisplaySize(usedBytes) + ", heap " + byteCountToDisplaySize(totalBytes) + ", max "
                + byteCountToDisplaySize(maxBytes) + "}";
    }

    /**
     * Converts byte count to human-readable size format.
     *
     * @param size the size in bytes

        assertEquals("1.024TB", MemoryUtil.byteCountToDisplaySize(FileUtils.ONE_TB));
        assertEquals("931.322TB", MemoryUtil.byteCountToDisplaySize(999_999_999_999_999L));
        assertEquals("931.322TB", MemoryUtil.byteCountToDisplaySize(1000_000_000_000_000L));
        assertEquals("1.024PB", MemoryUtil.byteCountToDisplaySize(FileUtils.ONE_PB));

            if (logger.isDebugEnabled()) {
                logger.debug("Added the document({}, {}ms). The number of a document cache is {}.",
                        MemoryUtil.byteCountToDisplaySize(contentSize), processingTime, docList.size());
            }

            if (docList.getContentSize() >= maxDocumentRequestSize || docList.size() >= maxDocumentCacheSize) {

                    logger.info("Sent {} docs (Doc:{process {}ms, send {}ms, size {}}, {})", docList.size(), docList.getProcessingTime(),
                            systemHelper.getCurrentTimeAsLong() - execTime, MemoryUtil.byteCountToDisplaySize(docList.getContentSize()),
                            MemoryUtil.getMemoryUsageLog());
                } else {

                    if (logger.isDebugEnabled()) {
                        logger.debug("Added the document({}, {}ms). The number of a document cache is {} (size: {}).",
                                MemoryUtil.byteCountToDisplaySize(contentSize), processingTime, docList.size(), docList.getContentSize());
                    }

                    if (docList.getContentSize() >= maxDocumentRequestSize) {