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MINOR: freq_ctr: add a function to add values with a peak

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Sometimes it's desirable to observe fading away peak values, where a new
value that is higher than the historical one instantly replaces it,
otherwise contributes to it. It is convenient when trying to observe
certain phenomenons like peak queue sizes. The new function
swrate_add_peak_local() does that to a private variable (no atomic ops
involved as it's not worth the cost since such use cases are typically
local).
This commit is contained in:
Willy Tarreau 2026-03-19 15:08:29 +01:00
parent fc38ebb079
commit eec60f14dd
1 changed files with 19 additions and 0 deletions
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19
include/haproxy/freq_ctr.h
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@ -403,6 +403,25 @@ static inline uint swrate_add_scaled_opportunistic(uint *sum, uint n, uint v, ui
return new_sum;
}
/* Like swrate_add() except that if <v> is beyond the current average, the
* average is replaced by the peak. This is essentially used to measure peak
* loads in the scheduler, reason why it is provided as a local variant that
* does not involve atomic operations.
*/
static inline uint swrate_add_peak_local(uint *sum, uint n, uint v)
{
uint old_sum, new_sum;
old_sum = *sum;
if (v * n > old_sum)
new_sum = v * n;
else
new_sum = old_sum - (old_sum + n - 1) / n + v;
*sum = new_sum;
return new_sum;
}
/* Returns the average sample value for the sum <sum> over a sliding window of
* <n> samples. Better if <n> is a power of two. It must be the same <n> as the
* one used above in all additions.