Squashed 'YCSB/' content from commit 4db84c8

git-subtree-dir: YCSB
git-subtree-split: 4db84c89465d4af216c8cef7fb9f2030ef367c2e
Merge commit '6a914f9d5be06174f0e9b25ce345532e5540395a' as 'YCSB'