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author | Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> | 2012-09-17 16:31:14 +0800 |
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committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2012-09-17 13:10:03 -0300 |
commit | 0007eceaceb11520071d053acfe06ee3326b1d13 (patch) | |
tree | d9b96c6a53c1ccca87222003e7c5c0e4b0f171a0 /tools/perf/util/stat.c | |
parent | 034a9265c289d5298bac7bfd824d3d5b9ec892b4 (diff) | |
download | op-kernel-dev-0007eceaceb11520071d053acfe06ee3326b1d13.zip op-kernel-dev-0007eceaceb11520071d053acfe06ee3326b1d13.tar.gz |
perf stat: Move stats related code to util/stat.c
Then, the code can be shared between kvm events and perf stat.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
[ Dong Hao <haodong@linux.vnet.ibm.com>: rebase it on acme's git tree ]
Signed-off-by: Dong Hao <haodong@linux.vnet.ibm.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1347870675-31495-3-git-send-email-haodong@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/stat.c')
-rw-r--r-- | tools/perf/util/stat.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c new file mode 100644 index 0000000..2374212 --- /dev/null +++ b/tools/perf/util/stat.c @@ -0,0 +1,57 @@ +#include <math.h> + +#include "stat.h" + +void update_stats(struct stats *stats, u64 val) +{ + double delta; + + stats->n++; + delta = val - stats->mean; + stats->mean += delta / stats->n; + stats->M2 += delta*(val - stats->mean); +} + +double avg_stats(struct stats *stats) +{ + return stats->mean; +} + +/* + * http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance + * + * (\Sum n_i^2) - ((\Sum n_i)^2)/n + * s^2 = ------------------------------- + * n - 1 + * + * http://en.wikipedia.org/wiki/Stddev + * + * The std dev of the mean is related to the std dev by: + * + * s + * s_mean = ------- + * sqrt(n) + * + */ +double stddev_stats(struct stats *stats) +{ + double variance, variance_mean; + + if (!stats->n) + return 0.0; + + variance = stats->M2 / (stats->n - 1); + variance_mean = variance / stats->n; + + return sqrt(variance_mean); +} + +double rel_stddev_stats(double stddev, double avg) +{ + double pct = 0.0; + + if (avg) + pct = 100.0 * stddev/avg; + + return pct; +} |