From: Timo Sirainen <timo.sirainen@dovecot.fi>
Date: Thu, 7 Dec 2017 22:54:51 +0000 (+0200)
Subject: lib: timing - Allow changing sample buffer size
X-Git-Tag: 2.3.0.rc1~114
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=92fc2c856dcc20dd886ce79d141efd678ace595c;p=thirdparty%2Fdovecot%2Fcore.git

lib: timing - Allow changing sample buffer size
---

diff --git a/src/lib/timing.c b/src/lib/timing.c
index 8749ea7846..60794cbe33 100644
--- a/src/lib/timing.c
+++ b/src/lib/timing.c
@@ -6,20 +6,32 @@
 
 /* In order to have a vaguely accurate 95th percentile, you need way
    more than 20 in your subsample. */
-#define TIMING_SUBSAMPLING_BUFFER (20*24) /* 20*24 fits in a page */
+#define TIMING_DEFAULT_SUBSAMPLING_BUFFER (20*24) /* 20*24 fits in a page */
 
 struct timing {
+	unsigned int sample_count;
 	unsigned int count;
 	bool     sorted;
 	uint64_t min;
-	uint64_t samples[TIMING_SUBSAMPLING_BUFFER];
 	uint64_t max;
 	uint64_t sum;
+	uint64_t samples[];
 };
 
 struct timing *timing_init(void)
 {
-	return i_new(struct timing, 1);
+	return timing_init_with_size(TIMING_DEFAULT_SUBSAMPLING_BUFFER);
+}
+
+struct timing *timing_init_with_size(unsigned int sample_count)
+{
+	i_assert(sample_count > 0);
+
+	struct timing *timing =
+		i_malloc(sizeof(struct timing) +
+			 sizeof(uint64_t) * sample_count);
+	timing->sample_count = sample_count;
+	return timing;
 }
 
 void timing_deinit(struct timing **_timing)
@@ -29,18 +41,20 @@ void timing_deinit(struct timing **_timing)
 
 void timing_reset(struct timing *timing)
 {
+	unsigned int sample_count = timing->sample_count;
 	i_zero(timing);
+	timing->sample_count = sample_count;
 }
 
 void timing_add_usecs(struct timing *timing, uint64_t usecs)
 {
-	if (timing->count < TIMING_SUBSAMPLING_BUFFER) {
+	if (timing->count < timing->sample_count) {
 		timing->samples[timing->count] = usecs;
 		if (timing->count == 0)
 			timing->min = timing->max = usecs;
 	} else {
 		unsigned int idx = i_rand_limit(timing->count);
-		if (idx < TIMING_SUBSAMPLING_BUFFER)
+		if (idx < timing->sample_count)
 			timing->samples[idx] = usecs;
 	}
 
@@ -86,9 +100,9 @@ static void timing_ensure_sorted(struct timing *timing)
 	if (timing->sorted)
 		return;
 
-	unsigned int count = (timing->count < TIMING_SUBSAMPLING_BUFFER)
+	unsigned int count = (timing->count < timing->sample_count)
 		? timing->count
-		: TIMING_SUBSAMPLING_BUFFER;
+		: timing->sample_count;
 	i_qsort(timing->samples, count, sizeof(*timing->samples),
 		uint64_cmp);
 	timing->sorted = TRUE;
@@ -100,9 +114,9 @@ uint64_t timing_get_median(const struct timing *timing)
 		return 0;
 	/* cast-away const - reading requires sorting */
 	timing_ensure_sorted((struct timing *)timing);
-	unsigned int count = (timing->count < TIMING_SUBSAMPLING_BUFFER)
+	unsigned int count = (timing->count < timing->sample_count)
 		? timing->count
-		: TIMING_SUBSAMPLING_BUFFER;
+		: timing->sample_count;
 	unsigned int idx1 = (count-1)/2, idx2 = count/2;
 	return (timing->samples[idx1] + timing->samples[idx2]) / 2;
 }
@@ -113,9 +127,9 @@ uint64_t timing_get_95th(const struct timing *timing)
 		return 0;
 	/* cast-away const - reading requires sorting */
 	timing_ensure_sorted((struct timing *)timing);
-	unsigned int count = (timing->count < TIMING_SUBSAMPLING_BUFFER)
+	unsigned int count = (timing->count < timing->sample_count)
 		? timing->count
-		: TIMING_SUBSAMPLING_BUFFER;
+		: timing->sample_count;
 	unsigned int idx = count - count/20 - 1;
 	return timing->samples[idx];
 }
diff --git a/src/lib/timing.h b/src/lib/timing.h
index 79536f9ed1..0d016b5b0e 100644
--- a/src/lib/timing.h
+++ b/src/lib/timing.h
@@ -2,6 +2,7 @@
 #define TIMING_H
 
 struct timing *timing_init(void);
+struct timing *timing_init_with_size(unsigned int sample_count);
 void timing_deinit(struct timing **timing);
 
 /* Reset all events. */