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0 us can be a valid percentile value if you're really fast #50

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0 us can be a valid percentile value if you're really fast #50

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65 changes: 46 additions & 19 deletions src/netlib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4376,14 +4376,32 @@ HIST_report(HIST h){

/* search buckets for each unit */
int
HIST_search_bucket(int *unit, int num, int *last, int *current, double scale){
HIST_search_bucket(int *unit,
int num,
int *last,
int *current,
double scale,
int * out_is_result_valid
){
int base = HIST_NUM_OF_BUCKET / 10;
int i;
for (i = 0; i < HIST_NUM_OF_BUCKET; i++){
*last = *current;
*current += unit[i];
if (*current >= num)
if (*current >= num){
/*
If e.g. 50% of the messages were faster than 1 us and you are looking
for P50_LATENCY, the first call with h->unit_usec will return 0, which
will be a valid result. If it is not recognized as such, another call
for h->ten_usec will be made. If (unit[i] == 0) at that point, then you
divide by zero because (*current >= num) is true and (*current == *last)
is also true. You get +/-inf, cast that to an int, which is undefined,
and return it. If (unit[i] > 0) then you carry on calculating some wrong
value, because you now include h->ten_usec[0], when you shouldn't.
*/
*out_is_result_valid = 1;
return (int)((i + (double)(num - *last)/(*current - *last)) * scale/base);
}
}
return 0;
}
Expand All @@ -4395,49 +4413,58 @@ HIST_get_percentile(HIST h, const double percentile){
int num = (int) win_kludge;
int last = 0;
int current = 0;
int result;
int result = 0;
int is_result_valid = 0;

if (!num)
return 0;

/* search in unit usec range */
result = HIST_search_bucket(h->unit_usec, num, &last, &current, 1e0);
if (result)
result = HIST_search_bucket(h->unit_usec, num, &last, &current, 1e0,
&is_result_valid);
if (is_result_valid)
return result;

/* search in ten usec range */
result = HIST_search_bucket(h->ten_usec, num, &last, &current, 1e1);
if (result)
result = HIST_search_bucket(h->ten_usec, num, &last, &current, 1e1,
&is_result_valid);
if (is_result_valid)
return result;

/* search in ten hundred usec range */
result = HIST_search_bucket(h->hundred_usec, num, &last, &current, 1e2);
if (result)
result = HIST_search_bucket(h->hundred_usec, num, &last, &current, 1e2,
&is_result_valid);
if (is_result_valid)
return result;

/* search in unic msec range */
result = HIST_search_bucket(h->unit_msec, num, &last, &current, 1e3);
if (result)
result = HIST_search_bucket(h->unit_msec, num, &last, &current, 1e3,
&is_result_valid);
if (is_result_valid)
return result;

/* search in ten msec range */
result = HIST_search_bucket(h->ten_msec, num, &last, &current, 1e4);
if (result)
result = HIST_search_bucket(h->ten_msec, num, &last, &current, 1e4,
&is_result_valid);
if (is_result_valid)
return result;

/* search in hundred msec range */
result = HIST_search_bucket(h->hundred_msec, num, &last, &current, 1e5);
if (result)
result = HIST_search_bucket(h->hundred_msec, num, &last, &current, 1e5,
&is_result_valid);
if (is_result_valid)
return result;

/* search in unit sec range */
result = HIST_search_bucket(h->unit_sec, num, &last, &current, 1e6);
if (result)
result = HIST_search_bucket(h->unit_sec, num, &last, &current, 1e6,
&is_result_valid);
if (is_result_valid)
return result;

/* search in ten sec range */
result = HIST_search_bucket(h->ten_sec, num, &last, &current, 1e7);
if (result)
result = HIST_search_bucket(h->ten_sec, num, &last, &current, 1e7,
&is_result_valid);
if (is_result_valid)
return result;

return (int)(1e8);
Expand Down