a significant performance drop for high concurrency bechmarks
(bug #11765850 - 58854).

Here's the comment of the patch commit:

The bug is that the InnoDB pre-fetch cache was not being used in
row_search_for_mysql().  Secondly the changeset that planted the
bug also introduced some inefficient code. It would read an extra
row, convert it to MySQL row format (for ICP==off), copy the row
to the pre-fetch cache row buffer, then check for cache overflow
and dequeue the row that was pushed if there was a possibility of
a cache overflow.