tracing: Add tracepoint benchmark tracepoint

In order to help benchmark the time tracepoints take, a new config
option is added called CONFIG_TRACEPOINT_BENCHMARK. When this option
is set a tracepoint is created called "benchmark:benchmark_event".
When the tracepoint is enabled, it kicks off a kernel thread that
goes into an infinite loop (calling cond_sched() to let other tasks
run), and calls the tracepoint. Each iteration will record the time
it took to write to the tracepoint and the next iteration that
data will be passed to the tracepoint itself. That is, the tracepoint
will report the time it took to do the previous tracepoint.
The string written to the tracepoint is a static string of 128 bytes
to keep the time the same. The initial string is simply a write of
"START". The second string records the cold cache time of the first
write which is not added to the rest of the calculations.

As it is a tight loop, it benchmarks as hot cache. That's fine because
we care most about hot paths that are probably in cache already.

An example of the output:

     START
     first=3672 [COLD CACHED]
     last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
     last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
     last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
     last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
     last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
     last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

path: root/debian/changelog

acpitail (0.1-2) unstable; urgency=low

  * Replaced obsolete dh_clean -k with dh_prep in rules.
  * Changed maintainer to Debian Acpi Team.
  * Removed Homepage tag in control in favour of the new control field.
  * Added Vcs-Git and Vcs-Browser fields to control.
  * Bumped Standards-Version to 3.8.0, no changes necessary.
  * Updated debhelper compatibility level from 5 to 7.

 -- Tobias Klauser <tklauser@distanz.ch>  Thu, 01 Jan 2009 15:40:49 +0100

acpitail (0.1-1) unstable; urgency=low

  * Initial release. (Closes: #430022)
  * Added manpage

 -- Tobias Klauser <tklauser@access.unizh.ch>  Sat, 04 Aug 2007 18:59:17 +0200