public boolean usable() {
        if (path.toFile().exists()) {
            return updateValues(time.milliseconds());
        } else {
            LOG.debug("Disabling IO metrics collection because {} does not exist.", path);
            return false;
        }
    }
Read /proc/self/io.
Generally, each line in this file contains a prefix followed by a colon and a number.
For example, it might contain this:
rchar: 4052
wchar: 0
syscr: 13
syscw: 0
read_bytes: 0
write_bytes: 0
cancelled_write_bytes: 0
server/src/main/java/org/apache/kafka/server/metrics/LinuxIoMetricsCollector.java