At Facebook, we have upgraded most of MySQL database tiers to 5.6, except very few tiers that have a special requirement -- very fast single threaded replication speed. As Oli mentioned, single threaded performance is worse in 5.6. The regression is actually not visible in most cases. For remote clients, the performance regression is almost negligible because network latency is longer than 5.1->5.
![Single thread performance regression in 5.6 - Replication](https://cdn-ak-scissors.b.st-hatena.com/image/square/f8fc9206c4cf7c9d0097277041dd72e1913b0873/height=288;version=1;width=512/https%3A%2F%2Fblogger.googleusercontent.com%2Fimg%2Fb%2FR29vZ2xl%2FAVvXsEiZTlCwwE4U9eFIoBB0Rf8rByIODMS7aBU-iu3pjpTeDgJVtF0UZCgquvTDeWvysXHWw_1kDSnAiu_tncYSzAor9ywxs0QWPQ2haCHjJQB7pbUFCGYlYW0pGI_86Os6InrVleDrKlziz3o%2Fw1200-h630-p-k-no-nu%2Freplication_speed_benchmark.png)