Serhiy, this is 64-bit specific. Antoine, as far as I can tell, the main use case is: "Don't make it look like migrating to Python 3 is a terrible performance downgrade."

As we discussed on the language summit this year [1], we have to be at least not worse to look appealing. This might be a flawed benchmark but people will make them anyway. In this particular case, there's internal usage at Twitter that unearthed it. The example is just a simplified repro.

Some perf degradations were expected, like switching text to Unicode. In this case, the end result computed by both 2.7 and 3.4 is the same so we should be able to address this.

[1] http://lwn.net/Articles/640224/