GCPでCloud Storageに溜まったウン十GBのデータを削除しようとして

$ gsutil rm -rf gs://path/to/backet/

としたのだけど、めちゃくちゃ時間がかかる

実行後、「-mを使うといいよ」というメッセージが見えたので、いったん中断してヘルプを読んでみる

$ gsutil help options
NAME
  options - Top-Level Command-Line Options

	(中略)

  -m          Causes supported operations (acl ch, acl set, cp, mv, rm, rsync,
			  and setmeta) to run in parallel. This can significantly improve
			  performance if you are performing operations on a large number of
			  files over a reasonably fast network connection.

			  gsutil performs the specified operation using a combination of
			  multi-threading and multi-processing, using a number of threads
			  and processors determined by the parallel_thread_count and
			  parallel_process_count values set in the boto configuration
			  file. You might want to experiment with these values, as the
			  best values can vary based on a number of factors, including
			  network speed, number of CPUs, and available memory.

			  Using the -m option may make your performance worse if you
			  are using a slower network, such as the typical network speeds
			  offered by non-business home network plans. It can also make
			  your performance worse for cases that perform all operations
			  locally (e.g., gsutil rsync, where both source and desination URLs
			  are on the local disk), because it can "thrash" your local disk.

			  If a download or upload operation using parallel transfer fails
			  before the entire transfer is complete (e.g. failing after 300 of
			  1000 files have been transferred), you will need to restart the
			  entire transfer.

			  Also, although most commands will normally fail upon encountering
			  an error when the -m flag is disabled, all commands will
			  continue to try all operations when -m is enabled with multiple
			  threads or processes, and the number of failed operations (if any)
			  will be reported at the end of the command's execution.

どうやら、acl ch, acl set, cp, mv, rm, rsync, setmetaの実行時は、並列実行が出来るらしい

$ gsutil -m rm -rf gs://path/to/backet/

これで速くなりました