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36 The Metrics library implements a mechanism by which *producers* can
37 publish numeric information for later querying by *consumers*. In
38 practice producers will typically be other libraries or primary
39 processes, whereas consumers will typically be applications.
41 Metrics themselves are statistics that are not generated by PMDs. Metric
42 information is populated using a push model, where producers update the
43 values contained within the metric library by calling an update function
44 on the relevant metrics. Consumers receive metric information by querying
45 the central metric data, which is held in shared memory.
47 For each metric, a separate value is maintained for each port id, and
48 when publishing metric values the producers need to specify which port is
49 being updated. In addition there is a special id ``RTE_METRICS_GLOBAL``
50 that is intended for global statistics that are not associated with any
51 individual device. Since the metrics library is self-contained, the only
52 restriction on port numbers is that they are less than ``RTE_MAX_ETHPORTS``
53 - there is no requirement for the ports to actually exist.
55 Initialising the library
56 ------------------------
58 Before the library can be used, it has to be initialized by calling
59 ``rte_metrics_init()`` which sets up the metric store in shared memory.
60 This is where producers will publish metric information to, and where
61 consumers will query it from.
65 rte_metrics_init(rte_socket_id());
67 This function **must** be called from a primary process, but otherwise
68 producers and consumers can be in either primary or secondary processes.
73 Metrics must first be *registered*, which is the way producers declare
74 the names of the metrics they will be publishing. Registration can either
75 be done individually, or a set of metrics can be registered as a group.
76 Individual registration is done using ``rte_metrics_reg_name()``:
80 id_1 = rte_metrics_reg_name("mean_bits_in");
81 id_2 = rte_metrics_reg_name("mean_bits_out");
82 id_3 = rte_metrics_reg_name("peak_bits_in");
83 id_4 = rte_metrics_reg_name("peak_bits_out");
85 or alternatively, a set of metrics can be registered together using
86 ``rte_metrics_reg_names()``:
90 const char * const names[] = {
91 "mean_bits_in", "mean_bits_out",
92 "peak_bits_in", "peak_bits_out",
94 id_set = rte_metrics_reg_names(&names[0], 4);
96 If the return value is negative, it means registration failed. Otherwise
97 the return value is the *key* for the metric, which is used when updating
98 values. A table mapping together these key values and the metrics' names
99 can be obtained using ``rte_metrics_get_names()``.
101 Updating metric values
102 ----------------------
104 Once registered, producers can update the metric for a given port using
105 the ``rte_metrics_update_value()`` function. This uses the metric key
106 that is returned when registering the metric, and can also be looked up
107 using ``rte_metrics_get_names()``.
111 rte_metrics_update_value(port_id, id_1, values[0]);
112 rte_metrics_update_value(port_id, id_2, values[1]);
113 rte_metrics_update_value(port_id, id_3, values[2]);
114 rte_metrics_update_value(port_id, id_4, values[3]);
116 if metrics were registered as a single set, they can either be updated
117 individually using ``rte_metrics_update_value()``, or updated together
118 using the ``rte_metrics_update_values()`` function:
122 rte_metrics_update_value(port_id, id_set, values[0]);
123 rte_metrics_update_value(port_id, id_set + 1, values[1]);
124 rte_metrics_update_value(port_id, id_set + 2, values[2]);
125 rte_metrics_update_value(port_id, id_set + 3, values[3]);
127 rte_metrics_update_values(port_id, id_set, values, 4);
129 Note that ``rte_metrics_update_values()`` cannot be used to update
130 metric values from *multiple* *sets*, as there is no guarantee two
131 sets registered one after the other have contiguous id values.
136 Consumers can obtain metric values by querying the metrics library using
137 the ``rte_metrics_get_values()`` function that return an array of
138 ``struct rte_metric_value``. Each entry within this array contains a metric
139 value and its associated key. A key-name mapping can be obtained using the
140 ``rte_metrics_get_names()`` function that returns an array of
141 ``struct rte_metric_name`` that is indexed by the key. The following will
142 print out all metrics for a given port:
146 void print_metrics() {
147 struct rte_metric_name *names;
150 len = rte_metrics_get_names(NULL, 0);
152 printf("Cannot get metrics count\n");
156 printf("No metrics to display (none have been registered)\n");
159 metrics = malloc(sizeof(struct rte_metric_value) * len);
160 names = malloc(sizeof(struct rte_metric_name) * len);
161 if (metrics == NULL || names == NULL) {
162 printf("Cannot allocate memory\n");
167 ret = rte_metrics_get_values(port_id, metrics, len);
168 if (ret < 0 || ret > len) {
169 printf("Cannot get metrics values\n");
174 printf("Metrics for port %i:\n", port_id);
175 for (i = 0; i < len; i++)
176 printf(" %s: %"PRIu64"\n",
177 names[metrics[i].key].name, metrics[i].value);
183 Bit-rate statistics library
184 ---------------------------
186 The bit-rate library calculates the exponentially-weighted moving
187 average and peak bit-rates for each active port (i.e. network device).
188 These statistics are reported via the metrics library using the
191 - ``mean_bits_in``: Average inbound bit-rate
192 - ``mean_bits_out``: Average outbound bit-rate
193 - ``ewma_bits_in``: Average inbound bit-rate (EWMA smoothed)
194 - ``ewma_bits_out``: Average outbound bit-rate (EWMA smoothed)
195 - ``peak_bits_in``: Peak inbound bit-rate
196 - ``peak_bits_out``: Peak outbound bit-rate
198 Once initialised and clocked at the appropriate frequency, these
199 statistics can be obtained by querying the metrics library.
204 Before the library can be used, it has to be initialised by calling
205 ``rte_stats_bitrate_create()``, which will return a bit-rate
206 calculation object. Since the bit-rate library uses the metrics library
207 to report the calculated statistics, the bit-rate library then needs to
208 register the calculated statistics with the metrics library. This is
209 done using the helper function ``rte_stats_bitrate_reg()``.
213 struct rte_stats_bitrates *bitrate_data;
215 bitrate_data = rte_stats_bitrate_create();
216 if (bitrate_data == NULL)
217 rte_exit(EXIT_FAILURE, "Could not allocate bit-rate data.\n");
218 rte_stats_bitrate_reg(bitrate_data);
220 Controlling the sampling rate
221 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
223 Since the library works by periodic sampling but does not use an
224 internal thread, the application has to periodically call
225 ``rte_stats_bitrate_calc()``. The frequency at which this function
226 is called should be the intended sampling rate required for the
227 calculated statistics. For instance if per-second statistics are
228 desired, this function should be called once a second.
232 tics_datum = rte_rdtsc();
233 tics_per_1sec = rte_get_timer_hz();
237 tics_current = rte_rdtsc();
238 if (tics_current - tics_datum >= tics_per_1sec) {
239 /* Periodic bitrate calculation */
240 for (idx_port = 0; idx_port < cnt_ports; idx_port++)
241 rte_stats_bitrate_calc(bitrate_data, idx_port);
242 tics_datum = tics_current;
248 Latency statistics library
249 --------------------------
251 The latency statistics library calculates the latency of packet
252 processing by a DPDK application, reporting the minimum, average,
253 and maximum nano-seconds that packet processing takes, as well as
254 the jitter in processing delay. These statistics are then reported
255 via the metrics library using the following names:
257 - ``min_latency_ns``: Minimum processing latency (nano-seconds)
258 - ``avg_latency_ns``: Average processing latency (nano-seconds)
259 - ``mac_latency_ns``: Maximum processing latency (nano-seconds)
260 - ``jitter_ns``: Variance in processing latency (nano-seconds)
262 Once initialised and clocked at the appropriate frequency, these
263 statistics can be obtained by querying the metrics library.
268 Before the library can be used, it has to be initialised by calling
269 ``rte_latencystats_init()``.
273 lcoreid_t latencystats_lcore_id = -1;
275 int ret = rte_latencystats_init(1, NULL);
277 rte_exit(EXIT_FAILURE, "Could not allocate latency data.\n");
280 Triggering statistic updates
281 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
283 The ``rte_latencystats_update()`` function needs to be called
284 periodically so that latency statistics can be updated.
288 if (latencystats_lcore_id == rte_lcore_id())
289 rte_latencystats_update();
294 When finished, ``rte_latencystats_uninit()`` needs to be called to
295 de-initialise the latency library.
299 rte_latencystats_uninit();