OProfile is a profiling system capable of profiling the whole system, include the kernel, kernel modules, libraries, and applications. If unsure, say N.
Instruction-Based Sampling (IBS) is a new profiling technique that provides rich, precise program performance information. IBS is introduced by AMD Family10h processors (AMD Opteron Quad-Core processor "Barcelona") to overcome the limitations of conventional performance counter sampling. If unsure, say N.
The number of hardware counters is limited. The multiplexing feature enables OProfile to gather more events than counters are provided by the hardware. This is realized by switching between events at an user specified time interval. If unsure, say N.
Kprobes allows you to trap at almost any kernel address and execute a callback function. register_kprobe() establishes a probepoint and specifies the callback. Kprobes is useful for kernel debugging, non-intrusive instrumentation and testing. If in doubt, say "N".
Some architectures are unable to perform unaligned accesses without the use of get_unaligned/put_unaligned. Others are unable to perform such accesses efficiently (e.g. trap on unaligned access and require fixing it up in the exception handler.) This symbol should be selected by an architecture if it can perform unaligned accesses efficiently to allow different code paths to be selected for these cases. Some network drivers, for example, could opt to not fix up alignment problems with received packets if doing so would not help much. See Documentation/unaligned-memory-access.txt for more information on the topic of unaligned memory accesses.
The <linux/clk.h> calls support software clock gating and thus are a key power management tool on many systems.