I was just wondering if anyone knew how many files the Drupal cron removes from your tmp/ directory per cron run? Is it limited to 100 at a time? Where can I see this information?
Yes, the query is set to 100 items per cron run. You can see the associated code for it in file_cron().
$fids = Drupal::entityQuery('file') ->accessCheck(FALSE) ->condition('status', FILE_STATUS_PERMANENT, '<>') ->condition('changed', REQUEST_TIME - $age, '<') ->range(0, 100) ->execute();