[MINOR] freq_ctr: add new types and functions for periods different from 1s
Some freq counters will have to work on periods different from 1 second.
The original freq counters rely on the period to be exactly one second.
The new ones (freq_ctr_period) let the user define the period in ticks,
and all computations are operated over that period. When reading a value,
it indicates the amount of events over that period too.
diff --git a/src/freq_ctr.c b/src/freq_ctr.c
index 3df930f..28f5936 100644
--- a/src/freq_ctr.c
+++ b/src/freq_ctr.c
@@ -1,7 +1,7 @@
/*
* Event rate calculation functions.
*
- * Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
+ * Copyright 2000-2010 Willy Tarreau <w@1wt.eu>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -110,6 +110,82 @@
return MAX(wait, 1);
}
+/* Reads a frequency counter taking history into account for missing time in
+ * current period. The period has to be passed in number of ticks and must
+ * match the one used to feed the counter. The counter value is reported for
+ * current date (now_ms). The return value has the same precision as one input
+ * data sample, so low rates over the period will be inaccurate but still
+ * appropriate for max checking. One trick we use for low values is to specially
+ * handle the case where the rate is between 0 and 1 in order to avoid flapping
+ * while waiting for the next event.
+ *
+ * For immediate limit checking, it's recommended to use freq_ctr_period_remain()
+ * instead which does not have the flapping correction, so that even frequencies
+ * as low as one event/period are properly handled.
+ *
+ * For measures over a 1-second period, it's better to use the implicit functions
+ * above.
+ */
+unsigned int read_freq_ctr_period(struct freq_ctr_period *ctr, unsigned int period)
+{
+ unsigned int curr, past;
+ unsigned int remain;
+
+ curr = ctr->curr_ctr;
+ past = ctr->prev_ctr;
+
+ remain = ctr->curr_tick + period - now_ms;
+ if (unlikely((int)remain < 0)) {
+ /* We're past the first period, check if we can still report a
+ * part of last period or if we're too far away.
+ */
+ remain += period;
+ if ((int)remain < 0)
+ return 0;
+ past = curr;
+ curr = 0;
+ }
+ if (past <= 1 && !curr)
+ return past; /* very low rate, avoid flapping */
+
+ curr += div64_32((unsigned long long)past * remain, period);
+ return curr;
+}
+
+/* Returns the number of remaining events that can occur on this freq counter
+ * while respecting <freq> events per period, and taking into account that
+ * <pend> events are already known to be pending. Returns 0 if limit was reached.
+ */
+unsigned int freq_ctr_remain_period(struct freq_ctr_period *ctr, unsigned int period,
+ unsigned int freq, unsigned int pend)
+{
+ unsigned int curr, past;
+ unsigned int remain;
+
+ curr = ctr->curr_ctr;
+ past = ctr->prev_ctr;
+
+ remain = ctr->curr_tick + period - now_ms;
+ if (likely((int)remain < 0)) {
+ /* We're past the first period, check if we can still report a
+ * part of last period or if we're too far away.
+ */
+ past = curr;
+ curr = 0;
+ remain += period;
+ if ((int)remain < 0)
+ past = 0;
+ }
+ if (likely(past))
+ curr += div64_32((unsigned long long)past * remain, period);
+
+ curr += pend;
+ freq -= curr;
+ if ((int)freq < 0)
+ freq = 0;
+ return freq;
+}
+
/*
* Local variables: