Bug#563847: Please enable the f-trace tracers

[dann frazier <dannf@debian.org>]

On Tue, Jan 05, 2010 at 12:53:23PM -0700, Troy Heber wrote:
> Source: linux-2.6
> Version: 2.6.32-3
> Severity: wishlist
> 
> Currently Ftrace is enabled in the kernel, CONFIG_FTRACE=y and
> CONFIG_DYNAMIC_FTRACE=y. However, some the most useful tracers, such
> as CONFIG_FUNCTION_TRACER and CONFIG_STACK_TRACER, are disabled. For
> example:
> 
> 	CONFIG_FTRACE=y
> 	# CONFIG_FUNCTION_TRACER is not set
> 	# CONFIG_IRQSOFF_TRACER is not set
> 	# CONFIG_SYSPROF_TRACER is not set
> 	# CONFIG_SCHED_TRACER is not set
> 	# CONFIG_FTRACE_SYSCALLS is not set
> 	...
> 	# CONFIG_POWER_TRACER is not set
> 	# CONFIG_STACK_TRACER is not set
> 
> Since Dynamic Ftrace is already enabled, I can't think of down side to
> enabling the actual tracers. Please consider this a wishlist request
> to enabled them.

Of FUNCTION_TRACER, Kconfig says:
 If it's runtime disabled
   (the bootup default), then the overhead of the instructions is very
     small and not measurable even in micro-benchmarks.

And for STACK_TRACER:
 If this is configured with DYNAMIC_FTRACE then it will not have any
 overhead while the stack tracer is disabled.

So I've gone ahead and enabled them in svn.