code: private void checkEnoughMemSpace(StorageDir storageDir) {
      if (!OSUtils.isLinux()) {
        return;
      }
      List<UnixMountInfo> info;
      try {
        info = ShellUtils.getUnixMountInfo();
      } catch (IOException e) {
        LOG.warn("Failed to get mount information for verifying memory capacity: {}",
            e.getMessage());
        return;
      }
      boolean foundMountInfo = false;
      for (UnixMountInfo mountInfo : info) {
        Optional<String> mountPointOption = mountInfo.getMountPoint();
        Optional<String> fsTypeOption = mountInfo.getFsType();
        Optional<Long> sizeOption = mountInfo.getOptions().getSize();
        if (!mountPointOption.isPresent() || !fsTypeOption.isPresent() || !sizeOption.isPresent()) {
          continue;
        }
        String mountPoint = mountPointOption.get();
        String fsType = fsTypeOption.get();
        long size = sizeOption.get();
        try {
          // getDirPath gives something like "/mnt/tmpfs/alluxioworker".
          String rootStoragePath = PathUtils.getParent(storageDir.getDirPath());
          if (!PathUtils.cleanPath(mountPoint).equals(rootStoragePath)) {
            continue;
          }
        } catch (InvalidPathException e) {
          continue;
        }
        foundMountInfo = true;
        if ((fsType.equalsIgnoreCase("tmpfs") || fsType.equalsIgnoreCase("ramfs"))
            && size < storageDir.getCapacityBytes()) {
          throw new IllegalStateException(String.format(
              "%s is smaller than the configured size: %s size: %s, configured size: %s", fsType,
              fsType, FormatUtils.getSizeFromBytes(size),
              FormatUtils.getSizeFromBytes(storageDir.getCapacityBytes())));
        }
        break;
      }
      if (!foundMountInfo) {
        LOG.warn("Failed to verify memory capacity");
      }
    }
docs: Checks that a tmpfs/ramfs backing the storage directory has enough capacity. If the storage
  directory is not backed by tmpfs/ramfs or the size of the tmpfs/ramfs cannot be determined, a
  warning is logged but no exception is thrown.
  
  @param storageDir the storage dir to check
  @throws IllegalStateException if the tmpfs/ramfs is smaller than the configured memory size