2 // Copyright (c) 2010-2019 Intel Corporation
4 // Licensed under the Apache License, Version 2.0 (the "License");
5 // you may not use this file except in compliance with the License.
6 // You may obtain a copy of the License at
8 // http://www.apache.org/licenses/LICENSE-2.0
10 // Unless required by applicable law or agreed to in writing, software
11 // distributed under the License is distributed on an "AS IS" BASIS,
12 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 // See the License for the specific language governing permissions and
14 // limitations under the License.
17 #ifndef _HANDLE_LAT_H_
18 #define _HANDLE_LAT_H_
24 #include "task_base.h"
27 #define LATENCY_ACCURACY 1
28 // If ACCURACY_WINDOW is too small, the accuracy for packet N can be received by lat BEFORE
29 // packet N is received (re-ordering) resulting in accuracy being unused
30 // 8192 packets is equivalent to 550 micro-seconds at 10Gbps for 64 bytes packets
31 #define ACCURACY_WINDOW 8192
32 #define LAT_BUCKET_COUNT 128
34 #define LAT_BUCKET_COUNT 128
36 #define LAT_BUCKET_COUNT 128
39 uint64_t tot_all_pkts;
44 unsigned __int128 var_lat; /* variance */
45 uint64_t accuracy_limit_tsc;
47 uint64_t max_lat_error;
48 uint64_t min_lat_error;
49 uint64_t tot_lat_error;
50 unsigned __int128 var_lat_error;
52 uint64_t buckets[LAT_BUCKET_COUNT];
54 uint64_t lost_packets;
57 static struct time_unit lat_test_get_accuracy_limit(struct lat_test *lat_test)
59 return tsc_to_time_unit(lat_test->accuracy_limit_tsc);
62 static struct time_unit_err lat_test_get_avg(struct lat_test *lat_test)
67 tsc = lat_test->tot_lat/lat_test->tot_pkts;
68 tsc_error = lat_test->tot_lat_error/lat_test->tot_pkts;
70 struct time_unit_err ret = {
71 .time = tsc_to_time_unit(tsc),
72 .error = tsc_to_time_unit(tsc_error),
78 static struct time_unit_err lat_test_get_min(struct lat_test *lat_test)
80 struct time_unit_err ret = {
81 .time = tsc_to_time_unit(lat_test->min_lat),
82 .error = tsc_to_time_unit(lat_test->min_lat_error),
88 static struct time_unit_err lat_test_get_max(struct lat_test *lat_test)
90 struct time_unit_err ret = {
91 .time = tsc_to_time_unit(lat_test->max_lat),
92 .error = tsc_to_time_unit(lat_test->max_lat_error),
98 static struct time_unit_err lat_test_get_stddev(struct lat_test *lat_test)
100 unsigned __int128 avg_tsc = lat_test->tot_lat/lat_test->tot_pkts;
101 unsigned __int128 avg_tsc_squared = avg_tsc * avg_tsc;
102 unsigned __int128 avg_squares_tsc = lat_test->var_lat/lat_test->tot_pkts;
104 /* The assumption is that variance fits into 64 bits, meaning
105 that standard deviation fits into 32 bits. In other words,
106 the assumption is that the standard deviation is not more
107 than approximately 1 second. */
108 uint64_t var_tsc = avg_squares_tsc - avg_tsc_squared;
109 uint64_t stddev_tsc = sqrt(var_tsc);
111 unsigned __int128 avg_tsc_error = lat_test->tot_lat_error / lat_test->tot_pkts;
112 unsigned __int128 avg_tsc_squared_error = 2 * avg_tsc * avg_tsc_error + avg_tsc_error * avg_tsc_error;
113 unsigned __int128 avg_squares_tsc_error = lat_test->var_lat_error / lat_test->tot_pkts;
115 uint64_t var_tsc_error = avg_squares_tsc_error + avg_tsc_squared_error;
117 /* sqrt(a+-b) = sqrt(a) +- (-sqrt(a) + sqrt(a + b)) */
119 uint64_t stddev_tsc_error = - stddev_tsc + sqrt(var_tsc + var_tsc_error);
121 struct time_unit_err ret = {
122 .time = tsc_to_time_unit(stddev_tsc),
123 .error = tsc_to_time_unit(stddev_tsc_error),
129 static void _lat_test_histogram_combine(struct lat_test *dst, struct lat_test *src)
131 for (size_t i = 0; i < sizeof(dst->buckets)/sizeof(dst->buckets[0]); ++i)
132 dst->buckets[i] += src->buckets[i];
135 static void lat_test_combine(struct lat_test *dst, struct lat_test *src)
137 dst->tot_all_pkts += src->tot_all_pkts;
139 dst->tot_pkts += src->tot_pkts;
141 dst->tot_lat += src->tot_lat;
142 dst->tot_lat_error += src->tot_lat_error;
144 /* (a +- b)^2 = a^2 +- (2ab + b^2) */
145 dst->var_lat += src->var_lat;
146 dst->var_lat_error += src->var_lat_error;
148 if (src->max_lat > dst->max_lat) {
149 dst->max_lat = src->max_lat;
150 dst->max_lat_error = src->max_lat_error;
152 if (src->min_lat < dst->min_lat) {
153 dst->min_lat = src->min_lat;
154 dst->min_lat_error = src->min_lat_error;
157 if (src->accuracy_limit_tsc > dst->accuracy_limit_tsc)
158 dst->accuracy_limit_tsc = src->accuracy_limit_tsc;
159 dst->lost_packets += src->lost_packets;
161 #ifdef LATENCY_HISTOGRAM
162 _lat_test_histogram_combine(dst, src);
166 static void lat_test_reset(struct lat_test *lat_test)
168 lat_test->tot_all_pkts = 0;
169 lat_test->tot_pkts = 0;
170 lat_test->max_lat = 0;
171 lat_test->min_lat = -1;
172 lat_test->tot_lat = 0;
173 lat_test->var_lat = 0;
174 lat_test->max_lat_error = 0;
175 lat_test->min_lat_error = 0;
176 lat_test->tot_lat_error = 0;
177 lat_test->var_lat_error = 0;
178 lat_test->accuracy_limit_tsc = 0;
180 lat_test->lost_packets = 0;
182 memset(lat_test->buckets, 0, sizeof(lat_test->buckets));
185 static void lat_test_copy(struct lat_test *dst, struct lat_test *src)
187 if (src->tot_all_pkts)
188 memcpy(dst, src, sizeof(struct lat_test));
193 struct lat_test *task_lat_get_latency_meassurement(struct task_lat *task);
194 uint32_t task_lat_get_latency_bucket_size(struct task_lat *task);
195 void task_lat_use_other_latency_meassurement(struct task_lat *task);
196 void task_lat_set_accuracy_limit(struct task_lat *task, uint32_t accuracy_limit_nsec);
198 #endif /* _HANDLE_LAT_H_ */