From: Willy Tarreau <w@1wt.eu>
Date: Sun, 11 Apr 2021 08:42:28 +0000 (+0200)
Subject: MEDIUM: freq_ctr: reimplement freq_ctr_remain_period() from freq_ctr_total()
X-Git-Tag: v2.4-dev17~147
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=607be24a85f8c21c1d1528727e2e68f96f7d859b;p=thirdparty%2Fhaproxy.git

MEDIUM: freq_ctr: reimplement freq_ctr_remain_period() from freq_ctr_total()

Now the function becomes an inline one and only contains a divide and
a max. The divide will automatically go away with constant periods.
---

diff --git a/include/haproxy/freq_ctr.h b/include/haproxy/freq_ctr.h
index 6016614745..3060f2a12d 100644
--- a/include/haproxy/freq_ctr.h
+++ b/include/haproxy/freq_ctr.h
@@ -148,6 +148,20 @@ static inline uint read_freq_ctr_period(struct freq_ctr_period *ctr, uint period
  */
 unsigned int freq_ctr_remain(struct freq_ctr *ctr, unsigned int freq, unsigned int pend);
 
+/* 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.
+ */
+static inline uint freq_ctr_remain_period(struct freq_ctr_period *ctr, uint period, uint freq, uint pend)
+{
+	ullong total = freq_ctr_total(ctr, period, pend);
+	uint avg     = div64_32(total, period);
+
+	if (avg > freq)
+		avg = freq;
+	return freq - avg;
+}
+
 /* return the expected wait time in ms before the next event may occur,
  * respecting frequency <freq>, and assuming there may already be some pending
  * events. It returns zero if we can proceed immediately, otherwise the wait
@@ -158,8 +172,6 @@ unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned
 
 /* 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);
 
 /* While the functions above report average event counts per period, we are
  * also interested in average values per event. For this we use a different
diff --git a/src/freq_ctr.c b/src/freq_ctr.c
index a2ca040acd..d68a7841d9 100644
--- a/src/freq_ctr.c
+++ b/src/freq_ctr.c
@@ -166,56 +166,6 @@ unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned
 	return MAX(wait, 1);
 }
 
-/* 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, curr, past;
-	unsigned int remain, _curr_tick, curr_tick;
-
-	while (1) {
-		_curr = ctr->curr_ctr;
-		__ha_compiler_barrier();
-		_past = ctr->prev_ctr;
-		__ha_compiler_barrier();
-		_curr_tick = ctr->curr_tick;
-		__ha_compiler_barrier();
-		if (_curr_tick & 0x1)
-			continue;
-		curr = ctr->curr_ctr;
-		__ha_compiler_barrier();
-		past = ctr->prev_ctr;
-		__ha_compiler_barrier();
-		curr_tick = ctr->curr_tick;
-		__ha_compiler_barrier();
-		if (_curr == curr && _past == past && _curr_tick == curr_tick)
-			break;
-	};
-
-	remain = curr_tick + period - global_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;
-}
-
 /* Returns the total number of events over the current + last period, including
  * a number of already pending events <pend>. The average frequency will be
  * obtained by dividing the output by <period>. This is essentially made to