CONFIG_DEBUG_BFIN_HWTRACE_EXPAND is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

Expand Trace Buffer greater than 16 entries


Linux Kernel Configuration
└─>Kernel hacking
└─>Expand Trace Buffer greater than 16 entries
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
By selecting this option, every time the 16 hardware entries in
the Blackfin's HW Trace buffer are full, the kernel will move them
into a software buffer, for dumping when there is an issue. This
has a great impact on performance, (an interrupt every 16 change of
flows) and should normally be turned off, except in those nasty
debugging sessions