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authorJuri Lelli <juri.lelli@gmail.com>2013-06-12 12:03:18 +0200
committerSteven Rostedt <rostedt@goodmis.org>2013-06-19 23:32:09 -0400
commit52d85d763086594f139bf7d3a5641abeb91d9f57 (patch)
treeef1e85c2ac60076ecc3a31a60391653acff97e0b /crypto/michael_mic.c
parent195a84d91e92ee3fe571a2086a6db7e17bf5bc7c (diff)
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ftrace: Fix stddev calculation in function profiler
When FUNCTION_GRAPH_TRACER is enabled, ftrace can profile kernel functions and print basic statistics about them. Unfortunately, running stddev calculation is wrong. This patch corrects it implementing Welford’s method: s^2 = 1 / (n * (n-1)) * (n * \Sum (x_i)^2 - (\Sum x_i)^2) . Link: http://lkml.kernel.org/r/1371031398-24048-1-git-send-email-juri.lelli@gmail.com Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'crypto/michael_mic.c')
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