Summary: Ref T12646. - Use "wb1" instead of "wb" to use level 1 gzip compression (faster, less compressy). Locally, this went about 2x faster and the output only grew 4% larger. - LinesOfALargeExecFuture does a lot of unnecessary string operations, and can boil down to a busy wait. The process is pretty saturated by I/O so this isn't the end of the world, but just use raw ExecFuture with FutureIterator so that we wait in `select()`. - Also, nice the process to +19 so we try to give other things CPU. Test Plan: - Ran `bin/storage dump --compress --output ...`. - Saw CPU time for my local database drop from ~240s to ~90s, with a 4% larger output. Most of this was adding the `1`, but the ExecFuture thing helped a little, too. - I'm not sure what a great way to test `nice` in a local environment is and it's system dependent anyway, but nothing got worse / blew up. - Used `gzcat | head` and `gzcat | tail` on the result to sanity-check that everything was preserved. Reviewers: chad, amckinley Reviewed By: chad Maniphest Tasks: T12646 Differential Revision: https://secure.phabricator.com/D17795