Extended redis-benchmark instant metrics and overall latency report (#7600)

A first step to enable a consistent full percentile analysis on query latency so that we can fully understand the performance and stability characteristics of the redis-server system we are measuring. It also improves the instantaneous reported metrics, and the csv output format.

10 files changed, 2125 insertions, 56 deletions

diff --git a/deps/Makefile b/deps/Makefile
index 700867f3b..0815d15de 100644
--- a/deps/Makefile
+++ b/deps/Makefile
@@ -37,6 +37,7 @@ distclean:
 	-(cd linenoise && $(MAKE) clean) > /dev/null || true
 	-(cd lua && $(MAKE) clean) > /dev/null || true
 	-(cd jemalloc && [ -f Makefile ] && $(MAKE) distclean) > /dev/null || true
+	-(cd hdr_histogram && $(MAKE) clean) > /dev/null || true
 	-(rm -f .make-*)
 
 .PHONY: distclean
@@ -57,6 +58,12 @@ linenoise: .make-prerequisites
 
 .PHONY: linenoise
 
+hdr_histogram: .make-prerequisites
+	@printf '%b %b\n' $(MAKECOLOR)MAKE$(ENDCOLOR) $(BINCOLOR)$@$(ENDCOLOR)
+	cd hdr_histogram && $(MAKE)
+
+.PHONY: hdr_histogram
+
 ifeq ($(uname_S),SunOS)
 	# Make isinf() available
 	LUA_CFLAGS= -D__C99FEATURES__=1
diff --git a/deps/hdr_histogram/COPYING.txt b/deps/hdr_histogram/COPYING.txt
new file mode 100644
index 000000000..0e259d42c
--- /dev/null
+++ b/deps/hdr_histogram/COPYING.txt
@@ -0,0 +1,121 @@
+Creative Commons Legal Code
+
+CC0 1.0 Universal
+
+    CREATIVE COMMONS CORPORATION IS NOT A LAW FIRM AND DOES NOT PROVIDE
+    LEGAL SERVICES. DISTRIBUTION OF THIS DOCUMENT DOES NOT CREATE AN
+    ATTORNEY-CLIENT RELATIONSHIP. CREATIVE COMMONS PROVIDES THIS
+    INFORMATION ON AN "AS-IS" BASIS. CREATIVE COMMONS MAKES NO WARRANTIES
+    REGARDING THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS
+    PROVIDED HEREUNDER, AND DISCLAIMS LIABILITY FOR DAMAGES RESULTING FROM
+    THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS PROVIDED
+    HEREUNDER.
+
+Statement of Purpose
+
+The laws of most jurisdictions throughout the world automatically confer
+exclusive Copyright and Related Rights (defined below) upon the creator
+and subsequent owner(s) (each and all, an "owner") of an original work of
+authorship and/or a database (each, a "Work").
+
+Certain owners wish to permanently relinquish those rights to a Work for
+the purpose of contributing to a commons of creative, cultural and
+scientific works ("Commons") that the public can reliably and without fear
+of later claims of infringement build upon, modify, incorporate in other
+works, reuse and redistribute as freely as possible in any form whatsoever
+and for any purposes, including without limitation commercial purposes.
+These owners may contribute to the Commons to promote the ideal of a free
+culture and the further production of creative, cultural and scientific
+works, or to gain reputation or greater distribution for their Work in
+part through the use and efforts of others.
+
+For these and/or other purposes and motivations, and without any
+expectation of additional consideration or compensation, the person
+associating CC0 with a Work (the "Affirmer"), to the extent that he or she
+is an owner of Copyright and Related Rights in the Work, voluntarily
+elects to apply CC0 to the Work and publicly distribute the Work under its
+terms, with knowledge of his or her Copyright and Related Rights in the
+Work and the meaning and intended legal effect of CC0 on those rights.
+
+1. Copyright and Related Rights. A Work made available under CC0 may be
+protected by copyright and related or neighboring rights ("Copyright and
+Related Rights"). Copyright and Related Rights include, but are not
+limited to, the following:
+
+  i. the right to reproduce, adapt, distribute, perform, display,
+     communicate, and translate a Work;
+ ii. moral rights retained by the original author(s) and/or performer(s);
+iii. publicity and privacy rights pertaining to a person's image or
+     likeness depicted in a Work;
+ iv. rights protecting against unfair competition in regards to a Work,
+     subject to the limitations in paragraph 4(a), below;
+  v. rights protecting the extraction, dissemination, use and reuse of data
+     in a Work;
+ vi. database rights (such as those arising under Directive 96/9/EC of the
+     European Parliament and of the Council of 11 March 1996 on the legal
+     protection of databases, and under any national implementation
+     thereof, including any amended or successor version of such
+     directive); and
+vii. other similar, equivalent or corresponding rights throughout the
+     world based on applicable law or treaty, and any national
+     implementations thereof.
+
+2. Waiver. To the greatest extent permitted by, but not in contravention
+of, applicable law, Affirmer hereby overtly, fully, permanently,
+irrevocably and unconditionally waives, abandons, and surrenders all of
+Affirmer's Copyright and Related Rights and associated claims and causes
+of action, whether now known or unknown (including existing as well as
+future claims and causes of action), in the Work (i) in all territories
+worldwide, (ii) for the maximum duration provided by applicable law or
+treaty (including future time extensions), (iii) in any current or future
+medium and for any number of copies, and (iv) for any purpose whatsoever,
+including without limitation commercial, advertising or promotional
+purposes (the "Waiver"). Affirmer makes the Waiver for the benefit of each
+member of the public at large and to the detriment of Affirmer's heirs and
+successors, fully intending that such Waiver shall not be subject to
+revocation, rescission, cancellation, termination, or any other legal or
+equitable action to disrupt the quiet enjoyment of the Work by the public
+as contemplated by Affirmer's express Statement of Purpose.
+
+3. Public License Fallback. Should any part of the Waiver for any reason
+be judged legally invalid or ineffective under applicable law, then the
+Waiver shall be preserved to the maximum extent permitted taking into
+account Affirmer's express Statement of Purpose. In addition, to the
+extent the Waiver is so judged Affirmer hereby grants to each affected
+person a royalty-free, non transferable, non sublicensable, non exclusive,
+irrevocable and unconditional license to exercise Affirmer's Copyright and
+Related Rights in the Work (i) in all territories worldwide, (ii) for the
+maximum duration provided by applicable law or treaty (including future
+time extensions), (iii) in any current or future medium and for any number
+of copies, and (iv) for any purpose whatsoever, including without
+limitation commercial, advertising or promotional purposes (the
+"License"). The License shall be deemed effective as of the date CC0 was
+applied by Affirmer to the Work. Should any part of the License for any
+reason be judged legally invalid or ineffective under applicable law, such
+partial invalidity or ineffectiveness shall not invalidate the remainder
+of the License, and in such case Affirmer hereby affirms that he or she
+will not (i) exercise any of his or her remaining Copyright and Related
+Rights in the Work or (ii) assert any associated claims and causes of
+action with respect to the Work, in either case contrary to Affirmer's
+express Statement of Purpose.
+
+4. Limitations and Disclaimers.
+
+ a. No trademark or patent rights held by Affirmer are waived, abandoned,
+    surrendered, licensed or otherwise affected by this document.
+ b. Affirmer offers the Work as-is and makes no representations or
+    warranties of any kind concerning the Work, express, implied,
+    statutory or otherwise, including without limitation warranties of
+    title, merchantability, fitness for a particular purpose, non
+    infringement, or the absence of latent or other defects, accuracy, or
+    the present or absence of errors, whether or not discoverable, all to
+    the greatest extent permissible under applicable law.
+ c. Affirmer disclaims responsibility for clearing rights of other persons
+    that may apply to the Work or any use thereof, including without
+    limitation any person's Copyright and Related Rights in the Work.
+    Further, Affirmer disclaims responsibility for obtaining any necessary
+    consents, permissions or other rights required for any use of the
+    Work.
+ d. Affirmer understands and acknowledges that Creative Commons is not a
+    party to this document and has no duty or obligation with respect to
+    this CC0 or use of the Work.
diff --git a/deps/hdr_histogram/LICENSE.txt b/deps/hdr_histogram/LICENSE.txt
new file mode 100644
index 000000000..9b4e66ed7
--- /dev/null
+++ b/deps/hdr_histogram/LICENSE.txt
@@ -0,0 +1,41 @@
+The code in this repository code was Written by Gil Tene, Michael Barker,
+and Matt Warren, and released to the public domain, as explained at
+http://creativecommons.org/publicdomain/zero/1.0/
+
+For users of this code who wish to consume it under the "BSD" license
+rather than under the public domain or CC0 contribution text mentioned
+above, the code found under this directory is *also* provided under the
+following license (commonly referred to as the BSD 2-Clause License). This
+license does not detract from the above stated release of the code into
+the public domain, and simply represents an additional license granted by
+the Author.
+
+-----------------------------------------------------------------------------
+** Beginning of "BSD 2-Clause License" text. **
+
+ Copyright (c) 2012, 2013, 2014 Gil Tene
+ Copyright (c) 2014 Michael Barker
+ Copyright (c) 2014 Matt Warren
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ 1. Redistributions of source code must retain the above copyright notice,
+    this list of conditions and the following disclaimer.
+
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+    this list of conditions and the following disclaimer in the documentation
+    and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/deps/hdr_histogram/Makefile b/deps/hdr_histogram/Makefile
new file mode 100644
index 000000000..83d3760ae
--- /dev/null
+++ b/deps/hdr_histogram/Makefile
@@ -0,0 +1,20 @@
+STD=
+WARN= -Wall
+OPT= -Os
+
+R_CFLAGS= $(STD) $(WARN) $(OPT) $(DEBUG) $(CFLAGS)
+R_LDFLAGS= $(LDFLAGS)
+DEBUG= -g
+
+R_CC=$(CC) $(R_CFLAGS)
+R_LD=$(CC) $(R_LDFLAGS)
+
+hdr_histogram.o: hdr_histogram.h hdr_histogram.c 
+
+.c.o:
+	$(R_CC) -c  $< 
+
+clean:
+	rm -f *.o
+
+
diff --git a/deps/hdr_histogram/README.md b/deps/hdr_histogram/README.md
new file mode 100644
index 000000000..5f62c234c
--- /dev/null
+++ b/deps/hdr_histogram/README.md
@@ -0,0 +1,10 @@
+HdrHistogram_c v0.11.0
+
+----------------------------------------------
+
+This port contains a subset of the 'C' version of High Dynamic Range (HDR) Histogram available at [github.com/HdrHistogram/HdrHistogram_c](https://github.com/HdrHistogram/HdrHistogram_c).
+
+
+The code present on `hdr_histogram.c`, `hdr_histogram.h`, and `hdr_atomic.c` was Written by Gil Tene, Michael Barker,
+and Matt Warren, and released to the public domain, as explained at
+http://creativecommons.org/publicdomain/zero/1.0/.
\ No newline at end of file
diff --git a/deps/hdr_histogram/hdr_atomic.h b/deps/hdr_histogram/hdr_atomic.h
new file mode 100644
index 000000000..ae1056a83
--- /dev/null
+++ b/deps/hdr_histogram/hdr_atomic.h
@@ -0,0 +1,146 @@
+/**
+ * hdr_atomic.h
+ * Written by Philip Orwig and released to the public domain,
+ * as explained at http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+#ifndef HDR_ATOMIC_H__
+#define HDR_ATOMIC_H__
+
+
+#if defined(_MSC_VER)
+
+#include <stdint.h>
+#include <intrin.h>
+#include <stdbool.h>
+
+static void __inline * hdr_atomic_load_pointer(void** pointer)
+{
+	_ReadBarrier();
+	return *pointer;
+}
+
+static void hdr_atomic_store_pointer(void** pointer, void* value)
+{
+	_WriteBarrier();
+	*pointer = value;
+}
+
+static int64_t __inline hdr_atomic_load_64(int64_t* field)
+{ 
+	_ReadBarrier();
+	return *field;
+}
+
+static void __inline hdr_atomic_store_64(int64_t* field, int64_t value)
+{
+	_WriteBarrier();
+	*field = value;
+}
+
+static int64_t __inline hdr_atomic_exchange_64(volatile int64_t* field, int64_t value)
+{
+#if defined(_WIN64)
+    return _InterlockedExchange64(field, value);
+#else
+    int64_t comparand;
+    int64_t initial_value = *field;
+    do
+    {
+        comparand = initial_value;
+        initial_value = _InterlockedCompareExchange64(field, value, comparand);
+    }
+    while (comparand != initial_value);
+
+    return initial_value;
+#endif
+}
+
+static int64_t __inline hdr_atomic_add_fetch_64(volatile int64_t* field, int64_t value)
+{
+#if defined(_WIN64)
+	return _InterlockedExchangeAdd64(field, value) + value;
+#else
+    int64_t comparand;
+    int64_t initial_value = *field;
+    do
+    {
+        comparand = initial_value;
+        initial_value = _InterlockedCompareExchange64(field, comparand + value, comparand);
+    }
+    while (comparand != initial_value);
+
+    return initial_value + value;
+#endif
+}
+
+static bool __inline hdr_atomic_compare_exchange_64(volatile int64_t* field, int64_t* expected, int64_t desired)
+{
+    return *expected == _InterlockedCompareExchange64(field, desired, *expected);
+}
+
+#elif defined(__ATOMIC_SEQ_CST)
+
+#define hdr_atomic_load_pointer(x) __atomic_load_n(x, __ATOMIC_SEQ_CST)
+#define hdr_atomic_store_pointer(f,v) __atomic_store_n(f,v, __ATOMIC_SEQ_CST)
+#define hdr_atomic_load_64(x) __atomic_load_n(x, __ATOMIC_SEQ_CST)
+#define hdr_atomic_store_64(f,v) __atomic_store_n(f,v, __ATOMIC_SEQ_CST)
+#define hdr_atomic_exchange_64(f,i) __atomic_exchange_n(f,i, __ATOMIC_SEQ_CST)
+#define hdr_atomic_add_fetch_64(field, value) __atomic_add_fetch(field, value, __ATOMIC_SEQ_CST)
+#define hdr_atomic_compare_exchange_64(field, expected, desired) __atomic_compare_exchange_n(field, expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
+
+#elif defined(__x86_64__)
+
+#include <stdint.h>
+#include <stdbool.h>
+
+static inline void* hdr_atomic_load_pointer(void** pointer)
+{
+   void* p =  *pointer;
+	asm volatile ("" ::: "memory");
+	return p;
+}
+
+static inline void hdr_atomic_store_pointer(void** pointer, void* value)
+{
+    asm volatile ("lock; xchgq %0, %1" : "+q" (value), "+m" (*pointer));
+}
+
+static inline int64_t hdr_atomic_load_64(int64_t* field)
+{
+    int64_t i = *field;
+	asm volatile ("" ::: "memory");
+	return i;
+}
+
+static inline void hdr_atomic_store_64(int64_t* field, int64_t value)
+{
+    asm volatile ("lock; xchgq %0, %1" : "+q" (value), "+m" (*field));
+}
+
+static inline int64_t hdr_atomic_exchange_64(volatile int64_t* field, int64_t value)
+{
+    int64_t result = 0;
+    asm volatile ("lock; xchgq %1, %2" : "=r" (result), "+q" (value), "+m" (*field));
+    return result;
+}
+
+static inline int64_t hdr_atomic_add_fetch_64(volatile int64_t* field, int64_t value)
+{
+    return __sync_add_and_fetch(field, value);
+}
+
+static inline bool hdr_atomic_compare_exchange_64(volatile int64_t* field, int64_t* expected, int64_t desired)
+{
+    int64_t original;
+    asm volatile( "lock; cmpxchgq %2, %1" : "=a"(original), "+m"(*field) : "q"(desired), "0"(*expected));
+    return original == *expected;
+}
+
+#else
+
+#error "Unable to determine atomic operations for your platform"
+
+#endif
+
+#endif /* HDR_ATOMIC_H__ */
diff --git a/deps/hdr_histogram/hdr_histogram.c b/deps/hdr_histogram/hdr_histogram.c
new file mode 100644
index 000000000..5f5286f2f
--- /dev/null
+++ b/deps/hdr_histogram/hdr_histogram.c
@@ -0,0 +1,1155 @@
+/**
+ * hdr_histogram.c
+ * Written by Michael Barker and released to the public domain,
+ * as explained at http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <errno.h>
+#include <inttypes.h>
+
+#include "hdr_histogram.h"
+#include "hdr_atomic.h"
+
+/*  ######   #######  ##     ## ##    ## ########  ######  */
+/* ##    ## ##     ## ##     ## ###   ##    ##    ##    ## */
+/* ##       ##     ## ##     ## ####  ##    ##    ##       */
+/* ##       ##     ## ##     ## ## ## ##    ##     ######  */
+/* ##       ##     ## ##     ## ##  ####    ##          ## */
+/* ##    ## ##     ## ##     ## ##   ###    ##    ##    ## */
+/*  ######   #######   #######  ##    ##    ##     ######  */
+
+static int32_t normalize_index(const struct hdr_histogram* h, int32_t index)
+{
+    int32_t normalized_index;
+    int32_t adjustment = 0;
+    if (h->normalizing_index_offset == 0)
+    {
+        return index;
+    }
+
+    normalized_index = index - h->normalizing_index_offset;
+
+    if (normalized_index < 0)
+    {
+        adjustment = h->counts_len;
+    }
+    else if (normalized_index >= h->counts_len)
+    {
+        adjustment = -h->counts_len;
+    }
+
+    return normalized_index + adjustment;
+}
+
+static int64_t counts_get_direct(const struct hdr_histogram* h, int32_t index)
+{
+    return h->counts[index];
+}
+
+static int64_t counts_get_normalised(const struct hdr_histogram* h, int32_t index)
+{
+    return counts_get_direct(h, normalize_index(h, index));
+}
+
+static void counts_inc_normalised(
+    struct hdr_histogram* h, int32_t index, int64_t value)
+{
+    int32_t normalised_index = normalize_index(h, index);
+    h->counts[normalised_index] += value;
+    h->total_count += value;
+}
+
+static void counts_inc_normalised_atomic(
+    struct hdr_histogram* h, int32_t index, int64_t value)
+{
+    int32_t normalised_index = normalize_index(h, index);
+
+    hdr_atomic_add_fetch_64(&h->counts[normalised_index], value);
+    hdr_atomic_add_fetch_64(&h->total_count, value);
+}
+
+static void update_min_max(struct hdr_histogram* h, int64_t value)
+{
+    h->min_value = (value < h->min_value && value != 0) ? value : h->min_value;
+    h->max_value = (value > h->max_value) ? value : h->max_value;
+}
+
+static void update_min_max_atomic(struct hdr_histogram* h, int64_t value)
+{
+    int64_t current_min_value;
+    int64_t current_max_value;
+    do
+    {
+        current_min_value = hdr_atomic_load_64(&h->min_value);
+
+        if (0 == value || current_min_value <= value)
+        {
+            break;
+        }
+    }
+    while (!hdr_atomic_compare_exchange_64(&h->min_value, &current_min_value, value));
+
+    do
+    {
+        current_max_value = hdr_atomic_load_64(&h->max_value);
+
+        if (value <= current_max_value)
+        {
+            break;
+        }
+    }
+    while (!hdr_atomic_compare_exchange_64(&h->max_value, &current_max_value, value));
+}
+
+
+/* ##     ## ######## #### ##       #### ######## ##    ## */
+/* ##     ##    ##     ##  ##        ##     ##     ##  ##  */
+/* ##     ##    ##     ##  ##        ##     ##      ####   */
+/* ##     ##    ##     ##  ##        ##     ##       ##    */
+/* ##     ##    ##     ##  ##        ##     ##       ##    */
+/* ##     ##    ##     ##  ##        ##     ##       ##    */
+/*  #######     ##    #### ######## ####    ##       ##    */
+
+static int64_t power(int64_t base, int64_t exp)
+{
+    int64_t result = 1;
+    while(exp)
+    {
+        result *= base; exp--;
+    }
+    return result;
+}
+
+#if defined(_MSC_VER)
+#   if defined(_WIN64)
+#       pragma intrinsic(_BitScanReverse64)
+#   else
+#       pragma intrinsic(_BitScanReverse)
+#   endif
+#endif
+
+static int32_t count_leading_zeros_64(int64_t value)
+{
+#if defined(_MSC_VER)
+    uint32_t leading_zero = 0;
+#if defined(_WIN64)
+    _BitScanReverse64(&leading_zero, value);
+#else
+    uint32_t high = value >> 32;
+    if  (_BitScanReverse(&leading_zero, high))
+    {
+        leading_zero += 32;
+    }
+    else
+    {
+        uint32_t low = value & 0x00000000FFFFFFFF;
+        _BitScanReverse(&leading_zero, low);
+    }
+#endif
+    return 63 - leading_zero; /* smallest power of 2 containing value */
+#else
+    return __builtin_clzll(value); /* smallest power of 2 containing value */
+#endif
+}
+
+static int32_t get_bucket_index(const struct hdr_histogram* h, int64_t value)
+{
+    int32_t pow2ceiling = 64 - count_leading_zeros_64(value | h->sub_bucket_mask); /* smallest power of 2 containing value */
+    return pow2ceiling - h->unit_magnitude - (h->sub_bucket_half_count_magnitude + 1);
+}
+
+static int32_t get_sub_bucket_index(int64_t value, int32_t bucket_index, int32_t unit_magnitude)
+{
+    return (int32_t)(value >> (bucket_index + unit_magnitude));
+}
+
+static int32_t counts_index(const struct hdr_histogram* h, int32_t bucket_index, int32_t sub_bucket_index)
+{
+    /* Calculate the index for the first entry in the bucket: */
+    /* (The following is the equivalent of ((bucket_index + 1) * subBucketHalfCount) ): */
+    int32_t bucket_base_index = (bucket_index + 1) << h->sub_bucket_half_count_magnitude;
+    /* Calculate the offset in the bucket: */
+    int32_t offset_in_bucket = sub_bucket_index - h->sub_bucket_half_count;
+    /* The following is the equivalent of ((sub_bucket_index  - subBucketHalfCount) + bucketBaseIndex; */
+    return bucket_base_index + offset_in_bucket;
+}
+
+static int64_t value_from_index(int32_t bucket_index, int32_t sub_bucket_index, int32_t unit_magnitude)
+{
+    return ((int64_t) sub_bucket_index) << (bucket_index + unit_magnitude);
+}
+
+int32_t counts_index_for(const struct hdr_histogram* h, int64_t value)
+{
+    int32_t bucket_index     = get_bucket_index(h, value);
+    int32_t sub_bucket_index = get_sub_bucket_index(value, bucket_index, h->unit_magnitude);
+
+    return counts_index(h, bucket_index, sub_bucket_index);
+}
+
+int64_t hdr_value_at_index(const struct hdr_histogram *h, int32_t index)
+{
+    int32_t bucket_index = (index >> h->sub_bucket_half_count_magnitude) - 1;
+    int32_t sub_bucket_index = (index & (h->sub_bucket_half_count - 1)) + h->sub_bucket_half_count;
+
+    if (bucket_index < 0)
+    {
+        sub_bucket_index -= h->sub_bucket_half_count;
+        bucket_index = 0;
+    }
+
+    return value_from_index(bucket_index, sub_bucket_index, h->unit_magnitude);
+}
+
+int64_t hdr_size_of_equivalent_value_range(const struct hdr_histogram* h, int64_t value)
+{
+    int32_t bucket_index     = get_bucket_index(h, value);
+    int32_t sub_bucket_index = get_sub_bucket_index(value, bucket_index, h->unit_magnitude);
+    int32_t adjusted_bucket  = (sub_bucket_index >= h->sub_bucket_count) ? (bucket_index + 1) : bucket_index;
+    return INT64_C(1) << (h->unit_magnitude + adjusted_bucket);
+}
+
+static int64_t lowest_equivalent_value(const struct hdr_histogram* h, int64_t value)
+{
+    int32_t bucket_index     = get_bucket_index(h, value);
+    int32_t sub_bucket_index = get_sub_bucket_index(value, bucket_index, h->unit_magnitude);
+    return value_from_index(bucket_index, sub_bucket_index, h->unit_magnitude);
+}
+
+int64_t hdr_next_non_equivalent_value(const struct hdr_histogram *h, int64_t value)
+{
+    return lowest_equivalent_value(h, value) + hdr_size_of_equivalent_value_range(h, value);
+}
+
+static int64_t highest_equivalent_value(const struct hdr_histogram* h, int64_t value)
+{
+    return hdr_next_non_equivalent_value(h, value) - 1;
+}
+
+int64_t hdr_median_equivalent_value(const struct hdr_histogram *h, int64_t value)
+{
+    return lowest_equivalent_value(h, value) + (hdr_size_of_equivalent_value_range(h, value) >> 1);
+}
+
+static int64_t non_zero_min(const struct hdr_histogram* h)
+{
+    if (INT64_MAX == h->min_value)
+    {
+        return INT64_MAX;
+    }
+
+    return lowest_equivalent_value(h, h->min_value);
+}
+
+void hdr_reset_internal_counters(struct hdr_histogram* h)
+{
+    int min_non_zero_index = -1;
+    int max_index = -1;
+    int64_t observed_total_count = 0;
+    int i;
+
+    for (i = 0; i < h->counts_len; i++)
+    {
+        int64_t count_at_index;
+
+        if ((count_at_index = counts_get_direct(h, i)) > 0)
+        {
+            observed_total_count += count_at_index;
+            max_index = i;
+            if (min_non_zero_index == -1 && i != 0)
+            {
+                min_non_zero_index = i;
+            }
+        }
+    }
+
+    if (max_index == -1)
+    {
+        h->max_value = 0;
+    }
+    else
+    {
+        int64_t max_value = hdr_value_at_index(h, max_index);
+        h->max_value = highest_equivalent_value(h, max_value);
+    }
+
+    if (min_non_zero_index == -1)
+    {
+        h->min_value = INT64_MAX;
+    }
+    else
+    {
+        h->min_value = hdr_value_at_index(h, min_non_zero_index);
+    }
+
+    h->total_count = observed_total_count;
+}
+
+static int32_t buckets_needed_to_cover_value(int64_t value, int32_t sub_bucket_count, int32_t unit_magnitude)
+{
+    int64_t smallest_untrackable_value = ((int64_t) sub_bucket_count) << unit_magnitude;
+    int32_t buckets_needed = 1;
+    while (smallest_untrackable_value <= value)
+    {
+        if (smallest_untrackable_value > INT64_MAX / 2)
+        {
+            return buckets_needed + 1;
+        }
+        smallest_untrackable_value <<= 1;
+        buckets_needed++;
+    }
+
+    return buckets_needed;
+}
+
+/* ##     ## ######## ##     ##  #######  ########  ##    ## */
+/* ###   ### ##       ###   ### ##     ## ##     ##  ##  ##  */
+/* #### #### ##       #### #### ##     ## ##     ##   ####   */
+/* ## ### ## ######   ## ### ## ##     ## ########     ##    */
+/* ##     ## ##       ##     ## ##     ## ##   ##      ##    */
+/* ##     ## ##       ##     ## ##     ## ##    ##     ##    */
+/* ##     ## ######## ##     ##  #######  ##     ##    ##    */
+
+int hdr_calculate_bucket_config(
+        int64_t lowest_trackable_value,
+        int64_t highest_trackable_value,
+        int significant_figures,
+        struct hdr_histogram_bucket_config* cfg)
+{
+    int32_t sub_bucket_count_magnitude;
+    int64_t largest_value_with_single_unit_resolution;
+
+    if (lowest_trackable_value < 1 ||
+            significant_figures < 1 || 5 < significant_figures ||
+            lowest_trackable_value * 2 > highest_trackable_value)
+    {
+        return EINVAL;
+    }
+
+    cfg->lowest_trackable_value = lowest_trackable_value;
+    cfg->significant_figures = significant_figures;
+    cfg->highest_trackable_value = highest_trackable_value;
+
+    largest_value_with_single_unit_resolution = 2 * power(10, significant_figures);
+    sub_bucket_count_magnitude = (int32_t) ceil(log((double)largest_value_with_single_unit_resolution) / log(2));
+    cfg->sub_bucket_half_count_magnitude = ((sub_bucket_count_magnitude > 1) ? sub_bucket_count_magnitude : 1) - 1;
+
+    cfg->unit_magnitude = (int32_t) floor(log((double)lowest_trackable_value) / log(2));
+
+    cfg->sub_bucket_count      = (int32_t) pow(2, (cfg->sub_bucket_half_count_magnitude + 1));
+    cfg->sub_bucket_half_count = cfg->sub_bucket_count / 2;
+    cfg->sub_bucket_mask       = ((int64_t) cfg->sub_bucket_count - 1) << cfg->unit_magnitude;
+
+    if (cfg->unit_magnitude + cfg->sub_bucket_half_count_magnitude > 61)
+    {
+        return EINVAL;
+    }
+
+    cfg->bucket_count = buckets_needed_to_cover_value(highest_trackable_value, cfg->sub_bucket_count, (int32_t)cfg->unit_magnitude);
+    cfg->counts_len = (cfg->bucket_count + 1) * (cfg->sub_bucket_count / 2);
+
+    return 0;
+}
+
+void hdr_init_preallocated(struct hdr_histogram* h, struct hdr_histogram_bucket_config* cfg)
+{
+    h->lowest_trackable_value          = cfg->lowest_trackable_value;
+    h->highest_trackable_value         = cfg->highest_trackable_value;
+    h->unit_magnitude                  = (int32_t)cfg->unit_magnitude;
+    h->significant_figures             = (int32_t)cfg->significant_figures;
+    h->sub_bucket_half_count_magnitude = cfg->sub_bucket_half_count_magnitude;
+    h->sub_bucket_half_count           = cfg->sub_bucket_half_count;
+    h->sub_bucket_mask                 = cfg->sub_bucket_mask;
+    h->sub_bucket_count                = cfg->sub_bucket_count;
+    h->min_value                       = INT64_MAX;
+    h->max_value                       = 0;
+    h->normalizing_index_offset        = 0;
+    h->conversion_ratio                = 1.0;
+    h->bucket_count                    = cfg->bucket_count;
+    h->counts_len                      = cfg->counts_len;
+    h->total_count                     = 0;
+}
+
+int hdr_init(
+        int64_t lowest_trackable_value,
+        int64_t highest_trackable_value,
+        int significant_figures,
+        struct hdr_histogram** result)
+{
+    int64_t* counts;
+    struct hdr_histogram_bucket_config cfg;
+    struct hdr_histogram* histogram;
+
+    int r = hdr_calculate_bucket_config(lowest_trackable_value, highest_trackable_value, significant_figures, &cfg);
+    if (r)
+    {
+        return r;
+    }
+
+    counts = (int64_t*) calloc((size_t) cfg.counts_len, sizeof(int64_t));
+    if (!counts)
+    {
+        return ENOMEM;
+    }
+
+    histogram = (struct hdr_histogram*) calloc(1, sizeof(struct hdr_histogram));
+    if (!histogram)
+    {
+        free(counts);
+        return ENOMEM;
+    }
+
+    histogram->counts = counts;
+
+    hdr_init_preallocated(histogram, &cfg);
+    *result = histogram;
+
+    return 0;
+}
+
+void hdr_close(struct hdr_histogram* h)
+{
+    if (h) {
+	free(h->counts);
+	free(h);
+    }
+}
+
+int hdr_alloc(int64_t highest_trackable_value, int significant_figures, struct hdr_histogram** result)
+{
+    return hdr_init(1, highest_trackable_value, significant_figures, result);
+}
+
+/* reset a histogram to zero. */
+void hdr_reset(struct hdr_histogram *h)
+{
+     h->total_count=0;
+     h->min_value = INT64_MAX;
+     h->max_value = 0;
+     memset(h->counts, 0, (sizeof(int64_t) * h->counts_len));
+}
+
+size_t hdr_get_memory_size(struct hdr_histogram *h)
+{
+    return sizeof(struct hdr_histogram) + h->counts_len * sizeof(int64_t);
+}
+
+/* ##     ## ########  ########     ###    ######## ########  ######  */
+/* ##     ## ##     ## ##     ##   ## ##      ##    ##       ##    ## */
+/* ##     ## ##     ## ##     ##  ##   ##     ##    ##       ##       */
+/* ##     ## ########  ##     ## ##     ##    ##    ######    ######  */
+/* ##     ## ##        ##     ## #########    ##    ##             ## */
+/* ##     ## ##        ##     ## ##     ##    ##    ##       ##    ## */
+/*  #######  ##        ########  ##     ##    ##    ########  ######  */
+
+
+bool hdr_record_value(struct hdr_histogram* h, int64_t value)
+{
+    return hdr_record_values(h, value, 1);
+}
+
+bool hdr_record_value_atomic(struct hdr_histogram* h, int64_t value)
+{
+    return hdr_record_values_atomic(h, value, 1);
+}
+
+bool hdr_record_values(struct hdr_histogram* h, int64_t value, int64_t count)
+{
+    int32_t counts_index;
+
+    if (value < 0)
+    {
+        return false;
+    }
+
+    counts_index = counts_index_for(h, value);
+
+    if (counts_index < 0 || h->counts_len <= counts_index)
+    {
+        return false;
+    }
+
+    counts_inc_normalised(h, counts_index, count);
+    update_min_max(h, value);
+
+    return true;
+}
+
+bool hdr_record_values_atomic(struct hdr_histogram* h, int64_t value, int64_t count)
+{
+    int32_t counts_index;
+
+    if (value < 0)
+    {
+        return false;
+    }
+
+    counts_index = counts_index_for(h, value);
+
+    if (counts_index < 0 || h->counts_len <= counts_index)
+    {
+        return false;
+    }
+
+    counts_inc_normalised_atomic(h, counts_index, count);
+    update_min_max_atomic(h, value);
+
+    return true;
+}
+
+bool hdr_record_corrected_value(struct hdr_histogram* h, int64_t value, int64_t expected_interval)
+{
+    return hdr_record_corrected_values(h, value, 1, expected_interval);
+}
+
+bool hdr_record_corrected_value_atomic(struct hdr_histogram* h, int64_t value, int64_t expected_interval)
+{
+    return hdr_record_corrected_values_atomic(h, value, 1, expected_interval);
+}
+
+bool hdr_record_corrected_values(struct hdr_histogram* h, int64_t value, int64_t count, int64_t expected_interval)
+{
+    int64_t missing_value;
+
+    if (!hdr_record_values(h, value, count))
+    {
+        return false;
+    }
+
+    if (expected_interval <= 0 || value <= expected_interval)
+    {
+        return true;
+    }
+
+    missing_value = value - expected_interval;
+    for (; missing_value >= expected_interval; missing_value -= expected_interval)
+    {
+        if (!hdr_record_values(h, missing_value, count))
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+bool hdr_record_corrected_values_atomic(struct hdr_histogram* h, int64_t value, int64_t count, int64_t expected_interval)
+{
+    int64_t missing_value;
+
+    if (!hdr_record_values_atomic(h, value, count))
+    {
+        return false;
+    }
+
+    if (expected_interval <= 0 || value <= expected_interval)
+    {
+        return true;
+    }
+
+    missing_value = value - expected_interval;
+    for (; missing_value >= expected_interval; missing_value -= expected_interval)
+    {
+        if (!hdr_record_values_atomic(h, missing_value, count))
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+int64_t hdr_add(struct hdr_histogram* h, const struct hdr_histogram* from)
+{
+    struct hdr_iter iter;
+    int64_t dropped = 0;
+    hdr_iter_recorded_init(&iter, from);
+
+    while (hdr_iter_next(&iter))
+    {
+        int64_t value = iter.value;
+        int64_t count = iter.count;
+
+        if (!hdr_record_values(h, value, count))
+        {
+            dropped += count;
+        }
+    }
+
+    return dropped;
+}
+
+int64_t hdr_add_while_correcting_for_coordinated_omission(
+        struct hdr_histogram* h, struct hdr_histogram* from, int64_t expected_interval)
+{
+    struct hdr_iter iter;
+    int64_t dropped = 0;
+    hdr_iter_recorded_init(&iter, from);
+
+    while (hdr_iter_next(&iter))
+    {
+        int64_t value = iter.value;
+        int64_t count = iter.count;
+
+        if (!hdr_record_corrected_values(h, value, count, expected_interval))
+        {
+            dropped += count;
+        }
+    }
+
+    return dropped;
+}
+
+
+
+/* ##     ##    ###    ##       ##     ## ########  ######  */
+/* ##     ##   ## ##   ##       ##     ## ##       ##    ## */
+/* ##     ##  ##   ##  ##       ##     ## ##       ##       */
+/* ##     ## ##     ## ##       ##     ## ######    ######  */
+/*  ##   ##  ######### ##       ##     ## ##             ## */
+/*   ## ##   ##     ## ##       ##     ## ##       ##    ## */
+/*    ###    ##     ## ########  #######  ########  ######  */
+
+
+int64_t hdr_max(const struct hdr_histogram* h)
+{
+    if (0 == h->max_value)
+    {
+        return 0;
+    }
+
+    return highest_equivalent_value(h, h->max_value);
+}
+
+int64_t hdr_min(const struct hdr_histogram* h)
+{
+    if (0 < hdr_count_at_index(h, 0))
+    {
+        return 0;
+    }
+
+    return non_zero_min(h);
+}
+
+int64_t hdr_value_at_percentile(const struct hdr_histogram* h, double percentile)
+{
+    struct hdr_iter iter;
+    int64_t total = 0;
+    double requested_percentile = percentile < 100.0 ? percentile : 100.0;
+    int64_t count_at_percentile =
+        (int64_t) (((requested_percentile / 100) * h->total_count) + 0.5);
+    count_at_percentile = count_at_percentile > 1 ? count_at_percentile : 1;
+
+    hdr_iter_init(&iter, h);
+
+    while (hdr_iter_next(&iter))
+    {
+        total += iter.count;
+
+        if (total >= count_at_percentile)
+        {
+            int64_t value_from_index = iter.value;
+            return highest_equivalent_value(h, value_from_index);
+        }
+    }
+
+    return 0;
+}
+
+double hdr_mean(const struct hdr_histogram* h)
+{
+    struct hdr_iter iter;
+    int64_t total = 0;
+
+    hdr_iter_init(&iter, h);
+
+    while (hdr_iter_next(&iter))
+    {
+        if (0 != iter.count)
+        {
+            total += iter.count * hdr_median_equivalent_value(h, iter.value);
+        }
+    }
+
+    return (total * 1.0) / h->total_count;
+}
+
+double hdr_stddev(const struct hdr_histogram* h)
+{
+    double mean = hdr_mean(h);
+    double geometric_dev_total = 0.0;
+
+    struct hdr_iter iter;
+    hdr_iter_init(&iter, h);
+
+    while (hdr_iter_next(&iter))
+    {
+        if (0 != iter.count)
+        {
+            double dev = (hdr_median_equivalent_value(h, iter.value) * 1.0) - mean;
+            geometric_dev_total += (dev * dev) * iter.count;
+        }
+    }
+
+    return sqrt(geometric_dev_total / h->total_count);
+}
+
+bool hdr_values_are_equivalent(const struct hdr_histogram* h, int64_t a, int64_t b)
+{
+    return lowest_equivalent_value(h, a) == lowest_equivalent_value(h, b);
+}
+
+int64_t hdr_lowest_equivalent_value(const struct hdr_histogram* h, int64_t value)
+{
+    return lowest_equivalent_value(h, value);
+}
+
+int64_t hdr_count_at_value(const struct hdr_histogram* h, int64_t value)
+{
+    return counts_get_normalised(h, counts_index_for(h, value));
+}
+
+int64_t hdr_count_at_index(const struct hdr_histogram* h, int32_t index)
+{
+    return counts_get_normalised(h, index);
+}
+
+
+/* #### ######## ######## ########     ###    ########  #######  ########   ######  */
+/*  ##     ##    ##       ##     ##   ## ##      ##    ##     ## ##     ## ##    ## */
+/*  ##     ##    ##       ##     ##  ##   ##     ##    ##     ## ##     ## ##       */
+/*  ##     ##    ######   ########  ##     ##    ##    ##     ## ########   ######  */
+/*  ##     ##    ##       ##   ##   #########    ##    ##     ## ##   ##         ## */
+/*  ##     ##    ##       ##    ##  ##     ##    ##    ##     ## ##    ##  ##    ## */
+/* ####    ##    ######## ##     ## ##     ##    ##     #######  ##     ##  ######  */
+
+
+static bool has_buckets(struct hdr_iter* iter)
+{
+    return iter->counts_index < iter->h->counts_len;
+}
+
+static bool has_next(struct hdr_iter* iter)
+{
+    return iter->cumulative_count < iter->total_count;
+}
+
+static bool move_next(struct hdr_iter* iter)
+{
+    iter->counts_index++;
+
+    if (!has_buckets(iter))
+    {
+        return false;
+    }
+
+    iter->count = counts_get_normalised(iter->h, iter->counts_index);
+    iter->cumulative_count += iter->count;
+
+    iter->value = hdr_value_at_index(iter->h, iter->counts_index);
+    iter->highest_equivalent_value = highest_equivalent_value(iter->h, iter->value);
+    iter->lowest_equivalent_value = lowest_equivalent_value(iter->h, iter->value);
+    iter->median_equivalent_value = hdr_median_equivalent_value(iter->h, iter->value);
+
+    return true;
+}
+
+static int64_t peek_next_value_from_index(struct hdr_iter* iter)
+{
+    return hdr_value_at_index(iter->h, iter->counts_index + 1);
+}
+
+static bool next_value_greater_than_reporting_level_upper_bound(
+    struct hdr_iter *iter, int64_t reporting_level_upper_bound)
+{
+    if (iter->counts_index >= iter->h->counts_len)
+    {
+        return false;
+    }
+
+    return peek_next_value_from_index(iter) > reporting_level_upper_bound;
+}
+
+static bool basic_iter_next(struct hdr_iter *iter)
+{
+    if (!has_next(iter) || iter->counts_index >= iter->h->counts_len)
+    {
+        return false;
+    }
+
+    move_next(iter);
+
+    return true;
+}
+
+static void update_iterated_values(struct hdr_iter* iter, int64_t new_value_iterated_to)
+{
+    iter->value_iterated_from = iter->value_iterated_to;
+    iter->value_iterated_to = new_value_iterated_to;
+}
+
+static bool all_values_iter_next(struct hdr_iter* iter)
+{
+    bool result = move_next(iter);
+
+    if (result)
+    {
+        update_iterated_values(iter, iter->value);
+    }
+
+    return result;
+}
+
+void hdr_iter_init(struct hdr_iter* iter, const struct hdr_histogram* h)
+{
+    iter->h = h;
+
+    iter->counts_index = -1;
+    iter->total_count = h->total_count;
+    iter->count = 0;
+    iter->cumulative_count = 0;
+    iter->value = 0;
+    iter->highest_equivalent_value = 0;
+    iter->value_iterated_from = 0;
+    iter->value_iterated_to = 0;
+
+    iter->_next_fp = all_values_iter_next;
+}
+
+bool hdr_iter_next(struct hdr_iter* iter)
+{
+    return iter->_next_fp(iter);
+}
+
+/* ########  ######## ########   ######  ######## ##    ## ######## #### ##       ########  ######  */
+/* ##     ## ##       ##     ## ##    ## ##       ###   ##    ##     ##  ##       ##       ##    ## */
+/* ##     ## ##       ##     ## ##       ##       ####  ##    ##     ##  ##       ##       ##       */
+/* ########  ######   ########  ##       ######   ## ## ##    ##     ##  ##       ######    ######  */
+/* ##        ##       ##   ##   ##       ##       ##  ####    ##     ##  ##       ##             ## */
+/* ##        ##       ##    ##  ##    ## ##       ##   ###    ##     ##  ##       ##       ##    ## */
+/* ##        ######## ##     ##  ######  ######## ##    ##    ##    #### ######## ########  ######  */
+
+static bool percentile_iter_next(struct hdr_iter* iter)
+{
+    int64_t temp, half_distance, percentile_reporting_ticks;
+
+    struct hdr_iter_percentiles* percentiles = &iter->specifics.percentiles;
+
+    if (!has_next(iter))
+    {
+        if (percentiles->seen_last_value)
+        {
+            return false;
+        }
+
+        percentiles->seen_last_value = true;
+        percentiles->percentile = 100.0;
+
+        return true;
+    }
+
+    if (iter->counts_index == -1 && !basic_iter_next(iter))
+    {
+        return false;
+    }
+
+    do
+    {
+        double current_percentile = (100.0 * (double) iter->cumulative_count) / iter->h->total_count;
+        if (iter->count != 0 &&
+                percentiles->percentile_to_iterate_to <= current_percentile)
+        {
+            update_iterated_values(iter, highest_equivalent_value(iter->h, iter->value));
+
+            percentiles->percentile = percentiles->percentile_to_iterate_to;
+            temp = (int64_t)(log(100 / (100.0 - (percentiles->percentile_to_iterate_to))) / log(2)) + 1;
+            half_distance = (int64_t) pow(2, (double) temp);
+            percentile_reporting_ticks = percentiles->ticks_per_half_distance * half_distance;
+            percentiles->percentile_to_iterate_to += 100.0 / percentile_reporting_ticks;
+
+            return true;
+        }
+    }
+    while (basic_iter_next(iter));
+
+    return true;
+}
+
+void hdr_iter_percentile_init(struct hdr_iter* iter, const struct hdr_histogram* h, int32_t ticks_per_half_distance)
+{
+    iter->h = h;
+
+    hdr_iter_init(iter, h);
+
+    iter->specifics.percentiles.seen_last_value          = false;
+    iter->specifics.percentiles.ticks_per_half_distance  = ticks_per_half_distance;
+    iter->specifics.percentiles.percentile_to_iterate_to = 0.0;
+    iter->specifics.percentiles.percentile               = 0.0;
+
+    iter->_next_fp = percentile_iter_next;
+}
+
+static void format_line_string(char* str, size_t len, int significant_figures, format_type format)
+{
+#if defined(_MSC_VER)
+#define snprintf _snprintf
+#pragma warning(push)
+#pragma warning(disable: 4996)
+#endif
+    const char* format_str = "%s%d%s";
+
+    switch (format)
+    {
+        case CSV:
+            snprintf(str, len, format_str, "%.", significant_figures, "f,%f,%d,%.2f\n");
+            break;
+        case CLASSIC:
+            snprintf(str, len, format_str, "%12.", significant_figures, "f %12f %12d %12.2f\n");
+            break;
+        default:
+            snprintf(str, len, format_str, "%12.", significant_figures, "f %12f %12d %12.2f\n");
+    }
+#if defined(_MSC_VER)
+#undef snprintf
+#pragma warning(pop)
+#endif
+}
+
+
+/* ########  ########  ######   #######  ########  ########  ######## ########   */
+/* ##     ## ##       ##    ## ##     ## ##     ## ##     ## ##       ##     ##  */
+/* ##     ## ##       ##       ##     ## ##     ## ##     ## ##       ##     ##  */
+/* ########  ######   ##       ##     ## ########  ##     ## ######   ##     ##  */
+/* ##   ##   ##       ##       ##     ## ##   ##   ##     ## ##       ##     ##  */
+/* ##    ##  ##       ##    ## ##     ## ##    ##  ##     ## ##       ##     ##  */
+/* ##     ## ########  ######   #######  ##     ## ########  ######## ########   */
+
+
+static bool recorded_iter_next(struct hdr_iter* iter)
+{
+    while (basic_iter_next(iter))
+    {
+        if (iter->count != 0)
+        {
+            update_iterated_values(iter, iter->value);
+
+            iter->specifics.recorded.count_added_in_this_iteration_step = iter->count;
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void hdr_iter_recorded_init(struct hdr_iter* iter, const struct hdr_histogram* h)
+{
+    hdr_iter_init(iter, h);
+
+    iter->specifics.recorded.count_added_in_this_iteration_step = 0;
+
+    iter->_next_fp = recorded_iter_next;
+}
+
+/* ##       #### ##    ## ########    ###    ########  */
+/* ##        ##  ###   ## ##         ## ##   ##     ## */
+/* ##        ##  ####  ## ##        ##   ##  ##     ## */
+/* ##        ##  ## ## ## ######   ##     ## ########  */
+/* ##        ##  ##  #### ##       ######### ##   ##   */
+/* ##        ##  ##   ### ##       ##     ## ##    ##  */
+/* ######## #### ##    ## ######## ##     ## ##     ## */
+
+
+static bool iter_linear_next(struct hdr_iter* iter)
+{
+    struct hdr_iter_linear* linear = &iter->specifics.linear;
+
+    linear->count_added_in_this_iteration_step = 0;
+
+    if (has_next(iter) ||
+        next_value_greater_than_reporting_level_upper_bound(
+            iter, linear->next_value_reporting_level_lowest_equivalent))
+    {
+        do
+        {
+            if (iter->value >= linear->next_value_reporting_level_lowest_equivalent)
+            {
+                update_iterated_values(iter, linear->next_value_reporting_level);
+
+                linear->next_value_reporting_level += linear->value_units_per_bucket;
+                linear->next_value_reporting_level_lowest_equivalent =
+                    lowest_equivalent_value(iter->h, linear->next_value_reporting_level);
+
+                return true;
+            }
+
+            if (!move_next(iter))
+            {
+                return true;
+            }
+
+            linear->count_added_in_this_iteration_step += iter->count;
+        }
+        while (true);
+    }
+
+    return false;
+}
+
+
+void hdr_iter_linear_init(struct hdr_iter* iter, const struct hdr_histogram* h, int64_t value_units_per_bucket)
+{
+    hdr_iter_init(iter, h);
+
+    iter->specifics.linear.count_added_in_this_iteration_step = 0;
+    iter->specifics.linear.value_units_per_bucket = value_units_per_bucket;
+    iter->specifics.linear.next_value_reporting_level = value_units_per_bucket;
+    iter->specifics.linear.next_value_reporting_level_lowest_equivalent = lowest_equivalent_value(h, value_units_per_bucket);
+
+    iter->_next_fp = iter_linear_next;
+}
+
+void hdr_iter_linear_set_value_units_per_bucket(struct hdr_iter* iter, int64_t value_units_per_bucket)
+{
+    iter->specifics.linear.value_units_per_bucket = value_units_per_bucket;
+}
+
+/* ##        #######   ######      ###    ########  #### ######## ##     ## ##     ## ####  ######  */
+/* ##       ##     ## ##    ##    ## ##   ##     ##  ##     ##    ##     ## ###   ###  ##  ##    ## */
+/* ##       ##     ## ##         ##   ##  ##     ##  ##     ##    ##     ## #### ####  ##  ##       */
+/* ##       ##     ## ##   #### ##     ## ########   ##     ##    ######### ## ### ##  ##  ##       */
+/* ##       ##     ## ##    ##  ######### ##   ##    ##     ##    ##     ## ##     ##  ##  ##       */
+/* ##       ##     ## ##    ##  ##     ## ##    ##   ##     ##    ##     ## ##     ##  ##  ##    ## */
+/* ########  #######   ######   ##     ## ##     ## ####    ##    ##     ## ##     ## ####  ######  */
+
+static bool log_iter_next(struct hdr_iter *iter)
+{
+    struct hdr_iter_log* logarithmic = &iter->specifics.log;
+
+    logarithmic->count_added_in_this_iteration_step = 0;
+
+    if (has_next(iter) ||
+        next_value_greater_than_reporting_level_upper_bound(
+            iter, logarithmic->next_value_reporting_level_lowest_equivalent))
+    {
+        do
+        {
+            if (iter->value >= logarithmic->next_value_reporting_level_lowest_equivalent)
+            {
+                update_iterated_values(iter, logarithmic->next_value_reporting_level);
+
+                logarithmic->next_value_reporting_level *= (int64_t)logarithmic->log_base;
+                logarithmic->next_value_reporting_level_lowest_equivalent = lowest_equivalent_value(iter->h, logarithmic->next_value_reporting_level);
+
+                return true;
+            }
+
+            if (!move_next(iter))
+            {
+                return true;
+            }
+
+            logarithmic->count_added_in_this_iteration_step += iter->count;
+        }
+        while (true);
+    }
+
+    return false;
+}
+
+void hdr_iter_log_init(
+        struct hdr_iter* iter,
+        const struct hdr_histogram* h,
+        int64_t value_units_first_bucket,
+        double log_base)
+{
+    hdr_iter_init(iter, h);
+    iter->specifics.log.count_added_in_this_iteration_step = 0;
+    iter->specifics.log.log_base = log_base;
+    iter->specifics.log.next_value_reporting_level = value_units_first_bucket;
+    iter->specifics.log.next_value_reporting_level_lowest_equivalent = lowest_equivalent_value(h, value_units_first_bucket);
+
+    iter->_next_fp = log_iter_next;
+}
+
+/* Printing. */
+
+static const char* format_head_string(format_type format)
+{
+    switch (format)
+    {
+        case CSV:
+            return "%s,%s,%s,%s\n";
+        case CLASSIC:
+        default:
+            return "%12s %12s %12s %12s\n\n";
+    }
+}
+
+static const char CLASSIC_FOOTER[] =
+    "#[Mean    = %12.3f, StdDeviation   = %12.3f]\n"
+    "#[Max     = %12.3f, Total count    = %12" PRIu64 "]\n"
+    "#[Buckets = %12d, SubBuckets     = %12d]\n";
+
+int hdr_percentiles_print(
+        struct hdr_histogram* h, FILE* stream, int32_t ticks_per_half_distance,
+        double value_scale, format_type format)
+{
+    char line_format[25];
+    const char* head_format;
+    int rc = 0;
+    struct hdr_iter iter;
+    struct hdr_iter_percentiles * percentiles;
+
+    format_line_string(line_format, 25, h->significant_figures, format);
+    head_format = format_head_string(format);
+
+    hdr_iter_percentile_init(&iter, h, ticks_per_half_distance);
+
+    if (fprintf(
+            stream, head_format,
+            "Value", "Percentile", "TotalCount", "1/(1-Percentile)") < 0)
+    {
+        rc = EIO;
+        goto cleanup;
+    }
+
+    percentiles = &iter.specifics.percentiles;
+    while (hdr_iter_next(&iter))
+    {
+        double  value               = iter.highest_equivalent_value / value_scale;
+        double  percentile          = percentiles->percentile / 100.0;
+        int64_t total_count         = iter.cumulative_count;
+        double  inverted_percentile = (1.0 / (1.0 - percentile));
+
+        if (fprintf(
+                stream, line_format, value, percentile, total_count, inverted_percentile) < 0)
+        {
+            rc = EIO;
+            goto cleanup;
+        }
+    }
+
+    if (CLASSIC == format)
+    {
+        double mean   = hdr_mean(h)   / value_scale;
+        double stddev = hdr_stddev(h) / value_scale;
+        double max    = hdr_max(h)    / value_scale;
+
+        if (fprintf(
+                stream, CLASSIC_FOOTER,  mean, stddev, max,
+                h->total_count, h->bucket_count, h->sub_bucket_count) < 0)
+        {
+            rc = EIO;
+            goto cleanup;
+        }
+    }
+
+    cleanup:
+    return rc;
+}
diff --git a/deps/hdr_histogram/hdr_histogram.h b/deps/hdr_histogram/hdr_histogram.h
new file mode 100644
index 000000000..c26c56b20
--- /dev/null
+++ b/deps/hdr_histogram/hdr_histogram.h
@@ -0,0 +1,509 @@
+/**
+ * hdr_histogram.h
+ * Written by Michael Barker and released to the public domain,
+ * as explained at http://creativecommons.org/publicdomain/zero/1.0/
+ *
+ * The source for the hdr_histogram utilises a few C99 constructs, specifically
+ * the use of stdint/stdbool and inline variable declaration.
+ */
+
+#ifndef HDR_HISTOGRAM_H
+#define HDR_HISTOGRAM_H 1
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+struct hdr_histogram
+{
+    int64_t lowest_trackable_value;
+    int64_t highest_trackable_value;
+    int32_t unit_magnitude;
+    int32_t significant_figures;
+    int32_t sub_bucket_half_count_magnitude;
+    int32_t sub_bucket_half_count;
+    int64_t sub_bucket_mask;
+    int32_t sub_bucket_count;
+    int32_t bucket_count;
+    int64_t min_value;
+    int64_t max_value;
+    int32_t normalizing_index_offset;
+    double conversion_ratio;
+    int32_t counts_len;
+    int64_t total_count;
+    int64_t* counts;
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Allocate the memory and initialise the hdr_histogram.
+ *
+ * Due to the size of the histogram being the result of some reasonably
+ * involved math on the input parameters this function it is tricky to stack allocate.
+ * The histogram should be released with hdr_close
+ *
+ * @param lowest_trackable_value The smallest possible value to be put into the
+ * histogram.
+ * @param highest_trackable_value The largest possible value to be put into the
+ * histogram.
+ * @param significant_figures The level of precision for this histogram, i.e. the number
+ * of figures in a decimal number that will be maintained.  E.g. a value of 3 will mean
+ * the results from the histogram will be accurate up to the first three digits.  Must
+ * be a value between 1 and 5 (inclusive).
+ * @param result Output parameter to capture allocated histogram.
+ * @return 0 on success, EINVAL if lowest_trackable_value is < 1 or the
+ * significant_figure value is outside of the allowed range, ENOMEM if malloc
+ * failed.
+ */
+int hdr_init(
+    int64_t lowest_trackable_value,
+    int64_t highest_trackable_value,
+    int significant_figures,
+    struct hdr_histogram** result);
+
+/**
+ * Free the memory and close the hdr_histogram.
+ *
+ * @param h The histogram you want to close.
+ */
+void hdr_close(struct hdr_histogram* h);
+
+/**
+ * Allocate the memory and initialise the hdr_histogram.  This is the equivalent of calling
+ * hdr_init(1, highest_trackable_value, significant_figures, result);
+ *
+ * @deprecated use hdr_init.
+ */
+int hdr_alloc(int64_t highest_trackable_value, int significant_figures, struct hdr_histogram** result);
+
+
+/**
+ * Reset a histogram to zero - empty out a histogram and re-initialise it
+ *
+ * If you want to re-use an existing histogram, but reset everything back to zero, this
+ * is the routine to use.
+ *
+ * @param h The histogram you want to reset to empty.
+ *
+ */
+void hdr_reset(struct hdr_histogram* h);
+
+/**
+ * Get the memory size of the hdr_histogram.
+ *
+ * @param h "This" pointer
+ * @return The amount of memory used by the hdr_histogram in bytes
+ */
+size_t hdr_get_memory_size(struct hdr_histogram* h);
+
+/**
+ * Records a value in the histogram, will round this value of to a precision at or better
+ * than the significant_figure specified at construction time.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_value(struct hdr_histogram* h, int64_t value);
+
+/**
+ * Records a value in the histogram, will round this value of to a precision at or better
+ * than the significant_figure specified at construction time.
+ *
+ * Will record this value atomically, however the whole structure may appear inconsistent
+ * when read concurrently with this update.  Do NOT mix calls to this method with calls
+ * to non-atomic updates.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_value_atomic(struct hdr_histogram* h, int64_t value);
+
+/**
+ * Records count values in the histogram, will round this value of to a
+ * precision at or better than the significant_figure specified at construction
+ * time.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param count Number of 'value's to add to the histogram
+ * @return false if any value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_values(struct hdr_histogram* h, int64_t value, int64_t count);
+
+/**
+ * Records count values in the histogram, will round this value of to a
+ * precision at or better than the significant_figure specified at construction
+ * time.
+ *
+ * Will record this value atomically, however the whole structure may appear inconsistent
+ * when read concurrently with this update.  Do NOT mix calls to this method with calls
+ * to non-atomic updates.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param count Number of 'value's to add to the histogram
+ * @return false if any value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_values_atomic(struct hdr_histogram* h, int64_t value, int64_t count);
+
+/**
+ * Record a value in the histogram and backfill based on an expected interval.
+ *
+ * Records a value in the histogram, will round this value of to a precision at or better
+ * than the significant_figure specified at contruction time.  This is specifically used
+ * for recording latency.  If the value is larger than the expected_interval then the
+ * latency recording system has experienced co-ordinated omission.  This method fills in the
+ * values that would have occured had the client providing the load not been blocked.
+
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param expected_interval The delay between recording values.
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_corrected_value(struct hdr_histogram* h, int64_t value, int64_t expexcted_interval);
+
+/**
+ * Record a value in the histogram and backfill based on an expected interval.
+ *
+ * Records a value in the histogram, will round this value of to a precision at or better
+ * than the significant_figure specified at contruction time.  This is specifically used
+ * for recording latency.  If the value is larger than the expected_interval then the
+ * latency recording system has experienced co-ordinated omission.  This method fills in the
+ * values that would have occured had the client providing the load not been blocked.
+ *
+ * Will record this value atomically, however the whole structure may appear inconsistent
+ * when read concurrently with this update.  Do NOT mix calls to this method with calls
+ * to non-atomic updates.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param expected_interval The delay between recording values.
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_corrected_value_atomic(struct hdr_histogram* h, int64_t value, int64_t expexcted_interval);
+
+/**
+ * Record a value in the histogram 'count' times.  Applies the same correcting logic
+ * as 'hdr_record_corrected_value'.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param count Number of 'value's to add to the histogram
+ * @param expected_interval The delay between recording values.
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_corrected_values(struct hdr_histogram* h, int64_t value, int64_t count, int64_t expected_interval);
+
+/**
+ * Record a value in the histogram 'count' times.  Applies the same correcting logic
+ * as 'hdr_record_corrected_value'.
+ *
+ * Will record this value atomically, however the whole structure may appear inconsistent
+ * when read concurrently with this update.  Do NOT mix calls to this method with calls
+ * to non-atomic updates.
+ *
+ * @param h "This" pointer
+ * @param value Value to add to the histogram
+ * @param count Number of 'value's to add to the histogram
+ * @param expected_interval The delay between recording values.
+ * @return false if the value is larger than the highest_trackable_value and can't be recorded,
+ * true otherwise.
+ */
+bool hdr_record_corrected_values_atomic(struct hdr_histogram* h, int64_t value, int64_t count, int64_t expected_interval);
+
+/**
+ * Adds all of the values from 'from' to 'this' histogram.  Will return the
+ * number of values that are dropped when copying.  Values will be dropped
+ * if they around outside of h.lowest_trackable_value and
+ * h.highest_trackable_value.
+ *
+ * @param h "This" pointer
+ * @param from Histogram to copy values from.
+ * @return The number of values dropped when copying.
+ */
+int64_t hdr_add(struct hdr_histogram* h, const struct hdr_histogram* from);
+
+/**
+ * Adds all of the values from 'from' to 'this' histogram.  Will return the
+ * number of values that are dropped when copying.  Values will be dropped
+ * if they around outside of h.lowest_trackable_value and
+ * h.highest_trackable_value.
+ *
+ * @param h "This" pointer
+ * @param from Histogram to copy values from.
+ * @return The number of values dropped when copying.
+ */
+int64_t hdr_add_while_correcting_for_coordinated_omission(
+    struct hdr_histogram* h, struct hdr_histogram* from, int64_t expected_interval);
+
+/**
+ * Get minimum value from the histogram.  Will return 2^63-1 if the histogram
+ * is empty.
+ *
+ * @param h "This" pointer
+ */
+int64_t hdr_min(const struct hdr_histogram* h);
+
+/**
+ * Get maximum value from the histogram.  Will return 0 if the histogram
+ * is empty.
+ *
+ * @param h "This" pointer
+ */
+int64_t hdr_max(const struct hdr_histogram* h);
+
+/**
+ * Get the value at a specific percentile.
+ *
+ * @param h "This" pointer.
+ * @param percentile The percentile to get the value for
+ */
+int64_t hdr_value_at_percentile(const struct hdr_histogram* h, double percentile);
+
+/**
+ * Gets the standard deviation for the values in the histogram.
+ *
+ * @param h "This" pointer
+ * @return The standard deviation
+ */
+double hdr_stddev(const struct hdr_histogram* h);
+
+/**
+ * Gets the mean for the values in the histogram.
+ *
+ * @param h "This" pointer
+ * @return The mean
+ */
+double hdr_mean(const struct hdr_histogram* h);
+
+/**
+ * Determine if two values are equivalent with the histogram's resolution.
+ * Where "equivalent" means that value samples recorded for any two
+ * equivalent values are counted in a common total count.
+ *
+ * @param h "This" pointer
+ * @param a first value to compare
+ * @param b second value to compare
+ * @return 'true' if values are equivalent with the histogram's resolution.
+ */
+bool hdr_values_are_equivalent(const struct hdr_histogram* h, int64_t a, int64_t b);
+
+/**
+ * Get the lowest value that is equivalent to the given value within the histogram's resolution.
+ * Where "equivalent" means that value samples recorded for any two
+ * equivalent values are counted in a common total count.
+ *
+ * @param h "This" pointer
+ * @param value The given value
+ * @return The lowest value that is equivalent to the given value within the histogram's resolution.
+ */
+int64_t hdr_lowest_equivalent_value(const struct hdr_histogram* h, int64_t value);
+
+/**
+ * Get the count of recorded values at a specific value
+ * (to within the histogram resolution at the value level).
+ *
+ * @param h "This" pointer
+ * @param value The value for which to provide the recorded count
+ * @return The total count of values recorded in the histogram within the value range that is
+ * {@literal >=} lowestEquivalentValue(<i>value</i>) and {@literal <=} highestEquivalentValue(<i>value</i>)
+ */
+int64_t hdr_count_at_value(const struct hdr_histogram* h, int64_t value);
+
+int64_t hdr_count_at_index(const struct hdr_histogram* h, int32_t index);
+
+int64_t hdr_value_at_index(const struct hdr_histogram* h, int32_t index);
+
+struct hdr_iter_percentiles
+{
+    bool seen_last_value;
+    int32_t ticks_per_half_distance;
+    double percentile_to_iterate_to;
+    double percentile;
+};
+
+struct hdr_iter_recorded
+{
+    int64_t count_added_in_this_iteration_step;
+};
+
+struct hdr_iter_linear
+{
+    int64_t value_units_per_bucket;
+    int64_t count_added_in_this_iteration_step;
+    int64_t next_value_reporting_level;
+    int64_t next_value_reporting_level_lowest_equivalent;
+};
+
+struct hdr_iter_log
+{
+    double log_base;
+    int64_t count_added_in_this_iteration_step;
+    int64_t next_value_reporting_level;
+    int64_t next_value_reporting_level_lowest_equivalent;
+};
+
+/**
+ * The basic iterator.  This is a generic structure
+ * that supports all of the types of iteration.  Use
+ * the appropriate initialiser to get the desired
+ * iteration.
+ *
+ * @
+ */
+struct hdr_iter
+{
+    const struct hdr_histogram* h;
+    /** raw index into the counts array */
+    int32_t counts_index;
+    /** snapshot of the length at the time the iterator is created */
+    int64_t total_count;
+    /** value directly from array for the current counts_index */
+    int64_t count;
+    /** sum of all of the counts up to and including the count at this index */
+    int64_t cumulative_count;
+    /** The current value based on counts_index */
+    int64_t value;
+    int64_t highest_equivalent_value;
+    int64_t lowest_equivalent_value;
+    int64_t median_equivalent_value;
+    int64_t value_iterated_from;
+    int64_t value_iterated_to;
+
+    union
+    {
+        struct hdr_iter_percentiles percentiles;
+        struct hdr_iter_recorded recorded;
+        struct hdr_iter_linear linear;
+        struct hdr_iter_log log;
+    } specifics;
+
+    bool (* _next_fp)(struct hdr_iter* iter);
+
+};
+
+/**
+ * Initalises the basic iterator.
+ *
+ * @param itr 'This' pointer
+ * @param h The histogram to iterate over
+ */
+void hdr_iter_init(struct hdr_iter* iter, const struct hdr_histogram* h);
+
+/**
+ * Initialise the iterator for use with percentiles.
+ */
+void hdr_iter_percentile_init(struct hdr_iter* iter, const struct hdr_histogram* h, int32_t ticks_per_half_distance);
+
+/**
+ * Initialise the iterator for use with recorded values.
+ */
+void hdr_iter_recorded_init(struct hdr_iter* iter, const struct hdr_histogram* h);
+
+/**
+ * Initialise the iterator for use with linear values.
+ */
+void hdr_iter_linear_init(
+    struct hdr_iter* iter,
+    const struct hdr_histogram* h,
+    int64_t value_units_per_bucket);
+
+/**
+ * Update the iterator value units per bucket
+ */
+void hdr_iter_linear_set_value_units_per_bucket(struct hdr_iter* iter, int64_t value_units_per_bucket);
+
+/**
+ * Initialise the iterator for use with logarithmic values
+ */
+void hdr_iter_log_init(
+    struct hdr_iter* iter,
+    const struct hdr_histogram* h,
+    int64_t value_units_first_bucket,
+    double log_base);
+
+/**
+ * Iterate to the next value for the iterator.  If there are no more values
+ * available return faluse.
+ *
+ * @param itr 'This' pointer
+ * @return 'false' if there are no values remaining for this iterator.
+ */
+bool hdr_iter_next(struct hdr_iter* iter);
+
+typedef enum
+{
+    CLASSIC,
+    CSV
+} format_type;
+
+/**
+ * Print out a percentile based histogram to the supplied stream.  Note that
+ * this call will not flush the FILE, this is left up to the user.
+ *
+ * @param h 'This' pointer
+ * @param stream The FILE to write the output to
+ * @param ticks_per_half_distance The number of iteration steps per half-distance to 100%
+ * @param value_scale Scale the output values by this amount
+ * @param format_type Format to use, e.g. CSV.
+ * @return 0 on success, error code on failure.  EIO if an error occurs writing
+ * the output.
+ */
+int hdr_percentiles_print(
+    struct hdr_histogram* h, FILE* stream, int32_t ticks_per_half_distance,
+    double value_scale, format_type format);
+
+/**
+* Internal allocation methods, used by hdr_dbl_histogram.
+*/
+struct hdr_histogram_bucket_config
+{
+    int64_t lowest_trackable_value;
+    int64_t highest_trackable_value;
+    int64_t unit_magnitude;
+    int64_t significant_figures;
+    int32_t sub_bucket_half_count_magnitude;
+    int32_t sub_bucket_half_count;
+    int64_t sub_bucket_mask;
+    int32_t sub_bucket_count;
+    int32_t bucket_count;
+    int32_t counts_len;
+};
+
+int hdr_calculate_bucket_config(
+    int64_t lowest_trackable_value,
+    int64_t highest_trackable_value,
+    int significant_figures,
+    struct hdr_histogram_bucket_config* cfg);
+
+void hdr_init_preallocated(struct hdr_histogram* h, struct hdr_histogram_bucket_config* cfg);
+
+int64_t hdr_size_of_equivalent_value_range(const struct hdr_histogram* h, int64_t value);
+
+int64_t hdr_next_non_equivalent_value(const struct hdr_histogram* h, int64_t value);
+
+int64_t hdr_median_equivalent_value(const struct hdr_histogram* h, int64_t value);
+
+/**
+ * Used to reset counters after importing data manuallying into the histogram, used by the logging code
+ * and other custom serialisation tools.
+ */
+void hdr_reset_internal_counters(struct hdr_histogram* h);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/src/Makefile b/src/Makefile
index 3ca7b1685..a8d2aa518 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -16,7 +16,7 @@ release_hdr := $(shell sh -c './mkreleasehdr.sh')
 uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
 uname_M := $(shell sh -c 'uname -m 2>/dev/null || echo not')
 OPTIMIZATION?=-O2
-DEPENDENCY_TARGETS=hiredis linenoise lua
+DEPENDENCY_TARGETS=hiredis linenoise lua hdr_histogram
 NODEPS:=clean distclean
 
 # Default settings
@@ -149,7 +149,7 @@ endif
 endif
 endif
 # Include paths to dependencies
-FINAL_CFLAGS+= -I../deps/hiredis -I../deps/linenoise -I../deps/lua/src
+FINAL_CFLAGS+= -I../deps/hiredis -I../deps/linenoise -I../deps/lua/src -I../deps/hdr_histogram
 
 # Determine systemd support and/or build preference (defaulting to auto-detection)
 BUILD_WITH_SYSTEMD=no
@@ -300,7 +300,7 @@ $(REDIS_CLI_NAME): $(REDIS_CLI_OBJ)
 
 # redis-benchmark
 $(REDIS_BENCHMARK_NAME): $(REDIS_BENCHMARK_OBJ)
-	$(REDIS_LD) -o $@ $^ ../deps/hiredis/libhiredis.a $(FINAL_LIBS)
+	$(REDIS_LD) -o $@ $^ ../deps/hiredis/libhiredis.a ../deps/hdr_histogram/hdr_histogram.o $(FINAL_LIBS)
 
 dict-benchmark: dict.c zmalloc.c sds.c siphash.c
 	$(REDIS_CC) $(FINAL_CFLAGS) $^ -D DICT_BENCHMARK_MAIN -o $@ $(FINAL_LIBS)
diff --git a/src/redis-benchmark.c b/src/redis-benchmark.c
index a86079156..a221ebdd2 100644
--- a/src/redis-benchmark.c
+++ b/src/redis-benchmark.c
@@ -51,12 +51,17 @@
 #include "zmalloc.h"
 #include "atomicvar.h"
 #include "crc16_slottable.h"
+#include "hdr_histogram.h"
 
 #define UNUSED(V) ((void) V)
 #define RANDPTR_INITIAL_SIZE 8
-#define MAX_LATENCY_PRECISION 3
+#define DEFAULT_LATENCY_PRECISION 3
+#define MAX_LATENCY_PRECISION 4
 #define MAX_THREADS 500
 #define CLUSTER_SLOTS 16384
+#define CONFIG_LATENCY_HISTOGRAM_MIN_VALUE 10L          /* >= 10 usecs */
+#define CONFIG_LATENCY_HISTOGRAM_MAX_VALUE 3000000L          /* <= 30 secs(us precision) */
+#define CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE 3000000L   /* <= 3 secs(us precision) */
 
 #define CLIENT_GET_EVENTLOOP(c) \
     (c->thread_id >= 0 ? config.threads[c->thread_id]->el : config.el)
@@ -75,6 +80,9 @@ static struct config {
     int requests;
     int requests_issued;
     int requests_finished;
+    int previous_requests_finished;
+    int last_printed_bytes;
+    long long previous_tick;
     int keysize;
     int datasize;
     int randomkeys;
@@ -103,6 +111,8 @@ static struct config {
     int cluster_node_count;
     struct clusterNode **cluster_nodes;
     struct redisConfig *redis_config;
+    struct hdr_histogram* latency_histogram;
+    struct hdr_histogram* current_sec_latency_histogram;
     int is_fetching_slots;
     int is_updating_slots;
     int slots_last_update;
@@ -534,8 +544,23 @@ static void readHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
                 }
                 int requests_finished = 0;
                 atomicGetIncr(config.requests_finished, requests_finished, 1);
-                if (requests_finished < config.requests)
-                    config.latency[requests_finished] = c->latency;
+                if (requests_finished < config.requests){
+                        if (config.num_threads == 0) {
+                            hdr_record_value(
+                            config.latency_histogram,  // Histogram to record to
+                            (long)c->latency<=CONFIG_LATENCY_HISTOGRAM_MAX_VALUE ? (long)c->latency : CONFIG_LATENCY_HISTOGRAM_MAX_VALUE);  // Value to record
+                            hdr_record_value(
+                            config.current_sec_latency_histogram,  // Histogram to record to
+                            (long)c->latency<=CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE ? (long)c->latency : CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE);  // Value to record
+                        } else {
+                            hdr_record_value_atomic(
+                            config.latency_histogram,  // Histogram to record to
+                            (long)c->latency<=CONFIG_LATENCY_HISTOGRAM_MAX_VALUE ? (long)c->latency : CONFIG_LATENCY_HISTOGRAM_MAX_VALUE);  // Value to record
+                            hdr_record_value_atomic(
+                            config.current_sec_latency_histogram,  // Histogram to record to
+                            (long)c->latency<=CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE ? (long)c->latency : CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE);  // Value to record
+                        }
+                }
                 c->pending--;
                 if (c->pending == 0) {
                     clientDone(c);
@@ -794,27 +819,18 @@ static void createMissingClients(client c) {
     }
 }
 
-static int compareLatency(const void *a, const void *b) {
-    return (*(long long*)a)-(*(long long*)b);
-}
-
-static int ipow(int base, int exp) {
-    int result = 1;
-    while (exp) {
-        if (exp & 1) result *= base;
-        exp /= 2;
-        base *= base;
-    }
-    return result;
-}
-
 static void showLatencyReport(void) {
-    int i, curlat = 0;
-    int usbetweenlat = ipow(10, MAX_LATENCY_PRECISION-config.precision);
-    float perc, reqpersec;
 
-    reqpersec = (float)config.requests_finished/((float)config.totlatency/1000);
+    const float reqpersec = (float)config.requests_finished/((float)config.totlatency/1000.0f);
+    const float p0 = ((float) hdr_min(config.latency_histogram))/1000.0f;
+    const float p50 = hdr_value_at_percentile(config.latency_histogram, 50.0 )/1000.0f;
+    const float p95 = hdr_value_at_percentile(config.latency_histogram, 95.0 )/1000.0f;
+    const float p99 = hdr_value_at_percentile(config.latency_histogram, 99.0 )/1000.0f;
+    const float p100 = ((float) hdr_max(config.latency_histogram))/1000.0f;
+    const float avg = hdr_mean(config.latency_histogram)/1000.0f;
+
     if (!config.quiet && !config.csv) {
+        printf("%*s\r", config.last_printed_bytes, " "); // ensure there is a clean line
         printf("====== %s ======\n", config.title);
         printf("  %d requests completed in %.2f seconds\n", config.requests_finished,
             (float)config.totlatency/1000);
@@ -847,31 +863,52 @@ static void showLatencyReport(void) {
             printf("  threads: %d\n", config.num_threads);
 
         printf("\n");
-
-        qsort(config.latency,config.requests,sizeof(long long),compareLatency);
-        for (i = 0; i < config.requests; i++) {
-            if (config.latency[i]/usbetweenlat != curlat ||
-                i == (config.requests-1))
-            {
-                /* After the 2 milliseconds latency to have percentages split
-                 * by decimals will just add a lot of noise to the output. */
-                if (config.latency[i] >= 2000) {
-                    config.precision = 0;
-                    usbetweenlat = ipow(10,
-                        MAX_LATENCY_PRECISION-config.precision);
-                }
-
-                curlat = config.latency[i]/usbetweenlat;
-                perc = ((float)(i+1)*100)/config.requests;
-                printf("%.2f%% <= %.*f milliseconds\n", perc, config.precision,
-                    curlat/pow(10.0, config.precision));
+        printf("Latency by percentile distribution:\n");
+        struct hdr_iter iter;
+        long long previous_cumulative_count = -1;
+        const long long total_count = config.latency_histogram->total_count;
+        hdr_iter_percentile_init(&iter, config.latency_histogram, 1);
+        struct hdr_iter_percentiles *percentiles = &iter.specifics.percentiles;
+        while (hdr_iter_next(&iter))
+        {
+            const double value = iter.highest_equivalent_value / 1000.0f;
+            const double percentile = percentiles->percentile;
+            const long long cumulative_count = iter.cumulative_count;
+            if( previous_cumulative_count != cumulative_count || cumulative_count == total_count ){
+                printf("%3.3f%% <= %.3f milliseconds (cumulative count %lld)\n", percentile, value, cumulative_count);
             }
+            previous_cumulative_count = cumulative_count;
         }
-        printf("%.2f requests per second\n\n", reqpersec);
+        printf("\n");
+        printf("Cumulative distribution of latencies:\n");
+        previous_cumulative_count = -1;
+        hdr_iter_linear_init(&iter, config.latency_histogram, 100);
+        while (hdr_iter_next(&iter))
+        {
+            const double value = iter.highest_equivalent_value / 1000.0f;
+            const long long cumulative_count = iter.cumulative_count;
+            const double percentile = ((double)cumulative_count/(double)total_count)*100.0;
+            if( previous_cumulative_count != cumulative_count || cumulative_count == total_count ){
+                printf("%3.3f%% <= %.3f milliseconds (cumulative count %lld)\n", percentile, value, cumulative_count);
+            }
+            /* After the 2 milliseconds latency to have percentages split
+             * by decimals will just add a lot of noise to the output. */
+            if(iter.highest_equivalent_value > 2000){
+                hdr_iter_linear_set_value_units_per_bucket(&iter,1000);
+            }
+            previous_cumulative_count = cumulative_count;
+        }
+        printf("\n");
+        printf("Summary:\n");
+        printf("  throughput summary: %.2f requests per second\n", reqpersec);
+        printf("  latency summary (msec):\n");
+        printf("    %9s %9s %9s %9s %9s %9s\n", "avg", "min", "p50", "p95", "p99", "max");
+        printf("    %9.3f %9.3f %9.3f %9.3f %9.3f %9.3f\n", avg, p0, p50, p95, p99, p100);
     } else if (config.csv) {
-        printf("\"%s\",\"%.2f\"\n", config.title, reqpersec);
+        printf("\"%s\",\"%.2f\",\"%.3f\",\"%.3f\",\"%.3f\",\"%.3f\",\"%.3f\",\"%.3f\"\n", config.title, reqpersec, avg, p0, p50, p95, p99, p100);
     } else {
-        printf("%s: %.2f requests per second\n", config.title, reqpersec);
+        printf("%*s\r", config.last_printed_bytes, " "); // ensure there is a clean line
+        printf("%s: %.2f requests per second, p50=%.3f msec\n", config.title, reqpersec, p50);
     }
 }
 
@@ -904,6 +941,18 @@ static void benchmark(char *title, char *cmd, int len) {
     config.title = title;
     config.requests_issued = 0;
     config.requests_finished = 0;
+    config.previous_requests_finished = 0;
+    config.last_printed_bytes = 0;
+    hdr_init(
+        CONFIG_LATENCY_HISTOGRAM_MIN_VALUE,  // Minimum value
+        CONFIG_LATENCY_HISTOGRAM_MAX_VALUE,  // Maximum value
+        config.precision,  // Number of significant figures
+        &config.latency_histogram);  // Pointer to initialise
+    hdr_init(
+        CONFIG_LATENCY_HISTOGRAM_MIN_VALUE,  // Minimum value
+        CONFIG_LATENCY_HISTOGRAM_INSTANT_MAX_VALUE,  // Maximum value
+        config.precision,  // Number of significant figures
+        &config.current_sec_latency_histogram);  // Pointer to initialise
 
     if (config.num_threads) initBenchmarkThreads();
 
@@ -919,6 +968,9 @@ static void benchmark(char *title, char *cmd, int len) {
     showLatencyReport();
     freeAllClients();
     if (config.threads) freeBenchmarkThreads();
+    if (config.current_sec_latency_histogram) hdr_close(config.current_sec_latency_histogram);
+    if (config.latency_histogram) hdr_close(config.latency_histogram);
+
 }
 
 /* Thread functions. */
@@ -1387,7 +1439,7 @@ int parseOptions(int argc, const char **argv) {
         } else if (!strcmp(argv[i],"--precision")) {
             if (lastarg) goto invalid;
             config.precision = atoi(argv[++i]);
-            if (config.precision < 0) config.precision = 0;
+            if (config.precision < 0) config.precision = DEFAULT_LATENCY_PRECISION;
             if (config.precision > MAX_LATENCY_PRECISION) config.precision = MAX_LATENCY_PRECISION;
         } else if (!strcmp(argv[i],"--threads")) {
              if (lastarg) goto invalid;
@@ -1476,9 +1528,12 @@ int showThroughput(struct aeEventLoop *eventLoop, long long id, void *clientData
     UNUSED(clientData);
     int liveclients = 0;
     int requests_finished = 0;
+    int previous_requests_finished = 0;
+    long long current_tick = mstime();
     atomicGet(config.liveclients, liveclients);
     atomicGet(config.requests_finished, requests_finished);
-
+    atomicGet(config.previous_requests_finished, previous_requests_finished);
+    
     if (liveclients == 0 && requests_finished != config.requests) {
         fprintf(stderr,"All clients disconnected... aborting.\n");
         exit(1);
@@ -1493,9 +1548,14 @@ int showThroughput(struct aeEventLoop *eventLoop, long long id, void *clientData
         fflush(stdout);
 	return 250;
     }
-    float dt = (float)(mstime()-config.start)/1000.0;
-    float rps = (float)requests_finished/dt;
-    printf("%s: %.2f\r", config.title, rps);
+    const float dt = (float)(current_tick-config.start)/1000.0;
+    const float rps = (float)requests_finished/dt;
+    const float instantaneous_dt = (float)(current_tick-config.previous_tick)/1000.0;
+    const float instantaneous_rps = (float)(requests_finished-previous_requests_finished)/instantaneous_dt;
+    config.previous_tick = current_tick;
+    atomicSet(config.previous_requests_finished,requests_finished);
+    config.last_printed_bytes = printf("%s: rps=%.1f (overall: %.1f) avg_msec=%.3f (overall: %.3f)\r", config.title, instantaneous_rps, rps, hdr_mean(config.current_sec_latency_histogram)/1000.0f, hdr_mean(config.latency_histogram)/1000.0f);
+    hdr_reset(config.current_sec_latency_histogram);
     fflush(stdout);
     return 250; /* every 250ms */
 }
@@ -1540,7 +1600,6 @@ int main(int argc, const char **argv) {
     config.csv = 0;
     config.loop = 0;
     config.idlemode = 0;
-    config.latency = NULL;
     config.clients = listCreate();
     config.hostip = "127.0.0.1";
     config.hostport = 6379;
@@ -1548,7 +1607,7 @@ int main(int argc, const char **argv) {
     config.tests = NULL;
     config.dbnum = 0;
     config.auth = NULL;
-    config.precision = 1;
+    config.precision = DEFAULT_LATENCY_PRECISION;
     config.num_threads = 0;
     config.threads = NULL;
     config.cluster_mode = 0;
@@ -1564,8 +1623,6 @@ int main(int argc, const char **argv) {
     argc -= i;
     argv += i;
 
-    config.latency = zmalloc(sizeof(long long)*config.requests);
-
     if (config.cluster_mode) {
         /* Fetch cluster configuration. */
         if (!fetchClusterConfiguration() || !config.cluster_nodes) {
@@ -1611,7 +1668,6 @@ int main(int argc, const char **argv) {
         if (config.redis_config == NULL)
             fprintf(stderr, "WARN: could not fetch server CONFIG\n");
     }
-
     if (config.num_threads > 0) {
         pthread_mutex_init(&(config.requests_issued_mutex), NULL);
         pthread_mutex_init(&(config.requests_finished_mutex), NULL);
@@ -1639,7 +1695,9 @@ int main(int argc, const char **argv) {
         else aeMain(config.el);
         /* and will wait for every */
     }
-
+    if(config.csv){
+        printf("\"test\",\"rps\",\"avg_latency_ms\",\"min_latency_ms\",\"p50_latency_ms\",\"p95_latency_ms\",\"p99_latency_ms\",\"max_latency_ms\"\n");
+    }
     /* Run benchmark with command in the remainder of the arguments. */
     if (argc) {
         sds title = sdsnew(argv[0]);
@@ -1650,6 +1708,8 @@ int main(int argc, const char **argv) {
 
         do {
             len = redisFormatCommandArgv(&cmd,argc,argv,NULL);
+            // adjust the datasize to the parsed command
+            config.datasize = len;
             benchmark(title,cmd,len);
             free(cmd);
         } while(config.loop);