[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/include/proto/freq_ctr.h b/include/proto/freq_ctr.h
index 7add514..d85e721 100644
--- a/include/proto/freq_ctr.h
+++ b/include/proto/freq_ctr.h
@@ -56,6 +56,41 @@
/* Note: later we may want to propagate the update to other counters */
}
+/* Rotate a frequency counter when current period is over. Must not be called
+ * during a valid period. It is important that it correctly initializes a null
+ * area. This one works on frequency counters which have a period different
+ * from one second.
+ */
+static inline void rotate_freq_ctr_period(struct freq_ctr_period *ctr,
+ unsigned int period)
+{
+ ctr->prev_ctr = ctr->curr_ctr;
+ ctr->curr_tick += period;
+ if (likely(now_ms - ctr->curr_tick >= period)) {
+ /* we missed at least two periods */
+ ctr->prev_ctr = 0;
+ ctr->curr_tick = now_ms;
+ }
+ ctr->curr_ctr = 0; /* leave it at the end to help gcc optimize it away */
+}
+
+/* Update a frequency counter by <inc> incremental units. It is automatically
+ * rotated if the period is over. It is important that it correctly initializes
+ * a null area. This one works on frequency counters which have a period
+ * different from one second.
+ */
+static inline void update_freq_ctr_period(struct freq_ctr_period *ctr,
+ unsigned int period, unsigned int inc)
+{
+ if (likely(now_ms - ctr->curr_tick < period)) {
+ ctr->curr_ctr += inc;
+ return;
+ }
+ rotate_freq_ctr_period(ctr, period);
+ ctr->curr_ctr = inc;
+ /* Note: later we may want to propagate the update to other counters */
+}
+
/* Read a frequency counter taking history into account for missing time in
* current period.
*/
@@ -75,6 +110,11 @@
*/
unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned int pend);
+/* process freq counters over configurable periods */
+unsigned int read_freq_ctr_period(struct freq_ctr_period *ctr, unsigned int period);
+unsigned int freq_ctr_remain_period(struct freq_ctr_period *ctr, unsigned int period,
+ unsigned int freq, unsigned int pend);
+
#endif /* _PROTO_FREQ_CTR_H */
/*
diff --git a/include/types/freq_ctr.h b/include/types/freq_ctr.h
index a8cfbd7..425ddf3 100644
--- a/include/types/freq_ctr.h
+++ b/include/types/freq_ctr.h
@@ -1,35 +1,50 @@
/*
- include/types/freq_ctr.h
- This file contains structure declarations for frequency counters.
-
- Copyright (C) 2000-2009 Willy Tarreau - w@1wt.eu
-
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation, version 2.1
- exclusively.
-
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with this library; if not, write to the Free Software
- Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
-*/
+ * include/types/freq_ctr.h
+ * This file contains structure declarations for frequency counters.
+ *
+ * Copyright (C) 2000-2010 Willy Tarreau - w@1wt.eu
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
#ifndef _TYPES_FREQ_CTR_H
#define _TYPES_FREQ_CTR_H
#include <common/config.h>
+/* The implicit freq_ctr counter counts a rate of events per second. It is the
+ * preferred form to count rates over a one-second period, because it does not
+ * involve any divide.
+ */
struct freq_ctr {
unsigned int curr_sec; /* start date of current period (seconds from now.tv_sec) */
unsigned int curr_ctr; /* cumulated value for current period */
unsigned int prev_ctr; /* value for last period */
};
+/* The generic freq_ctr_period counter counts a rate of events per period, where
+ * the period has to be known by the user. The period is measured in ticks and
+ * must be at least 2 ticks long. This form is slightly more CPU intensive than
+ * the per-second form.
+ */
+struct freq_ctr_period {
+ unsigned int curr_tick; /* start date of current period (wrapping ticks) */
+ unsigned int curr_ctr; /* cumulated value for current period */
+ unsigned int prev_ctr; /* value for last period */
+};
+
#endif /* _TYPES_FREQ_CTR_H */
/*
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: