[PATCH 0/3] ftrace: fix stddev calculation and add a test for it

From: Juri Lelli
Date: Tue Jun 11 2013 - 05:09:35 EST

While profiling kernel functions via ftrace I noticed values of s^2 that
seemed odd. I implemented a test to verify correctness of averages and
s^2 calculations and proved the latter to be wrong. Then I fixed them up.

The first patch refactors function_stat_show() code a bit in order to be
able to implement the test (second patch). Third patch fixes up s^2
calculation (applying Welford's method).

Juri Lelli (3):
ftrace: refactor basis statistics calculation code
ftrace: test basic statistics calculation
ftrace: fix stddev calculation

kernel/trace/ftrace.c | 50 ++++++++++++++--------------
kernel/trace/trace.h | 16 +++++++++
kernel/trace/trace_selftest.c | 72 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 114 insertions(+), 24 deletions(-)


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