class type record_config =object..end
method bigblock_size : intMapred_def.mapred_job.bigblock_size. This is the
	requested size. The actual size is rounded up to the next
	multiple of filesystem blocks.method mr_buffer_size : intMapred_config.mapred_config.mr_buffer_size. Also
	rounded up.method mr_buffer_size_tight : intMapred_config.mapred_config.mr_buffer_size_tight.
	Also rounded up.