Perform a simple test comparing static and running (implemented by function_stat_calc()) average and stddev calculations.
Signed-off-by: Juri Lelli <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Ingo Molnar <[email protected]> --- kernel/trace/trace_selftest.c | 72 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index 2901e3b..e8ecb9a 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -4,6 +4,7 @@ #include <linux/kthread.h> #include <linux/delay.h> #include <linux/slab.h> +#include <linux/random.h> static inline int trace_valid_entry(struct trace_entry *entry) { @@ -724,6 +725,74 @@ static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace) } /* + * Test the trace basic running statistic calculations to see if they + * agree with static one. + */ +#define TIME_ENTRIES 50 +#define MAX_DURATION 1000000 /* ns */ + +static int trace_test_stat(void) +{ + unsigned long long time_array[TIME_ENTRIES]; + unsigned long long averages[TIME_ENTRIES], stddevs[TIME_ENTRIES]; + int i, j, count; + unsigned long long avg, stddev; + struct ftrace_profile rec; + + /* + * Fill-up time_array, each element corresponds to the time spent + * executing some function. + */ + for (i = 0; i < TIME_ENTRIES; i++) { + get_random_bytes(&time_array[i], sizeof(unsigned long long)); + time_array[i] %= MAX_DURATION; + averages[i] = stddevs[i] = 0; + } + + /* + * Calculate stats in the static way. + */ + for (i = 0; i < TIME_ENTRIES; i++) { + if (i == 0) { + averages[i] = time_array[i]; + stddevs[i] = 0; + continue; + } + + count = 0; + for (j = 0; j < i + 1; j++) { + count++; + averages[i] += time_array[j]; + } + do_div(averages[i], count); + + for (j = 0; j < count; j++) + stddevs[i] += (time_array[j] - averages[i]) * + (time_array[j] - averages[i]); + /* Reflect ns^2 -> us^2 conversion. */ + do_div(stddevs[i], (count - 1) * 1000); + } + + /* + * Now do the same using running stats and compare results. + */ + rec.time = rec.time_squared = 0; + + for (i = 0; i < TIME_ENTRIES; i++) { + avg = stddev = 0; + rec.counter = i + 1; + rec.time += time_array[i]; + rec.time_squared += time_array[i] * time_array[i]; + function_stat_calc(&rec, &avg, &stddev); + + if (avg != averages[i] || stddev != stddevs[i]) + return 1; + } + + return 0; +} + +/* * Pretty much the same than for the function tracer from which the selftest * has been borrowed. */ @@ -774,6 +843,9 @@ trace_selftest_startup_function_graph(struct tracer *trace, /* Don't test dynamic tracing, the function tracer already did */ + /* Check basic statistics */ + ret = trace_test_stat(); + out: /* Stop it if we failed */ if (ret) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
