@CanIgnoreReturnValue
    public Builder setMaxCacheSize(long maxCacheSize) {
      checkArgument(maxCacheSize >= 0, "maxCacheSize (%s) may not be negative", maxCacheSize);
      this.maxCacheSize = maxCacheSize;
      return this;
    }
Sets the maximum amount of unused space (in bytes) in the file system's in-memory file
storage that should be cached for reuse. By default, this will be equal to the {@linkplain
#setMaxSize(long) maximum size} of the storage, meaning that all space that is freed when
files are truncated or deleted is cached for reuse. This helps to avoid lots of garbage
collection when creating and deleting many files quickly. This can be set to 0 to disable
caching entirely (all freed blocks become available for garbage collection) or to some other
number to put an upper bound on the maximum amount of unused space the file system will keep
around.

<p>Like the maximum size, the actual value will be the closest multiple of the block size
that is less than or equal to the given size.
jimfs/src/main/java/com/google/common/jimfs/Configuration.java