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MINOR: stats: Prepare for more accurate moving averages

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Add swrate_add_dynamic function which is similar to swrate_add, but more
accurate when calculating moving averages when not enough samples have
been processed yet.
This commit is contained in:
Marcin Deranek 2020-05-15 18:26:18 +02:00 committed by Willy Tarreau
parent 5eb5e253e6
commit 4dc2b57d51
1 changed files with 18 additions and 0 deletions
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18
include/proto/freq_ctr.h
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@ -263,6 +263,24 @@ static inline unsigned int swrate_add(unsigned int *sum, unsigned int n, unsigne
return new_sum;
}
/* Adds sample value <v> to sliding window sum <sum> configured for <n> samples.
* The sample is returned. Better if <n> is a power of two. This function is
* thread-safe.
* This function should give better accuracy than swrate_add when number of
* samples collected is lower than nominal window size. In such circumstances
* <n> should be set to 0.
*/
static inline unsigned int swrate_add_dynamic(unsigned int *sum, unsigned int n, unsigned int v)
{
unsigned int new_sum, old_sum;
old_sum = *sum;
do {
new_sum = old_sum - (n ? (old_sum + n - 1) / n : 0) + v;
} while (!_HA_ATOMIC_CAS(sum, &old_sum, new_sum));
return new_sum;
}
/* Adds sample value <v> spanning <s> samples to sliding window sum <sum>
* configured for <n> samples, where <n> is supposed to be "much larger" than
* <s>. The sample is returned. Better if <n> is a power of two. Note that this