1 .. SPDX-License-Identifier: BSD-3-Clause
2 Copyright(c) 2017 Intel Corporation.
4 Service Cores Sample Application
5 ================================
7 The service cores sample application demonstrates the service cores capabilities
8 of DPDK. The service cores infrastructure is part of the DPDK EAL, and allows
9 any DPDK component to register a service. A service is a work item or task, that
10 requires CPU time to perform its duty.
12 This sample application registers 5 dummy services. These 5 services are used
13 to show how the service_cores API can be used to orchestrate these services to
14 run on different service lcores. This orchestration is done by calling the
15 service cores APIs, however the sample application introduces a "profile"
16 concept to contain the service mapping details. Note that the profile concept
17 is application specific, and not a part of the service cores API.
20 Compiling the Application
21 -------------------------
23 #. Go to the example directory:
25 .. code-block:: console
27 export RTE_SDK=/path/to/rte_sdk
28 cd ${RTE_SDK}/examples/service_cores
30 #. Set the target (a default target is used if not specified). For example:
32 .. code-block:: console
34 export RTE_TARGET=x86_64-native-linux-gcc
36 See the *DPDK Getting Started* Guide for possible RTE_TARGET values.
38 #. Build the application:
40 .. code-block:: console
44 Running the Application
45 -----------------------
47 To run the example, just execute the binary. Since the application dynamically
48 adds service cores in the application code itself, there is no requirement to
49 pass a service core-mask as an EAL argument at startup time.
51 .. code-block:: console
53 $ ./build/service_cores
59 The following sections provide some explanation of code focusing on
60 registering applications from an applications point of view, and modifying the
61 service core counts and mappings at runtime.
67 The following code section shows how to register a service as an application.
68 Note that the service component header must be included by the application in
69 order to register services: ``rte_service_component.h``, in addition
70 to the ordinary service cores header ``rte_service.h`` which provides
71 the runtime functions to add, remove and remap service cores.
75 struct rte_service_spec service = {
76 .name = "service_name",
78 int ret = rte_service_component_register(services, &id);
82 /* set the service itself to be ready to run. In the case of
83 * ethdev, eventdev etc PMDs, this will be set when the
84 * appropriate configure or setup function is called.
86 rte_service_component_runstate_set(id, 1);
88 /* Collect statistics for the service */
89 rte_service_set_stats_enable(id, 1);
91 /* The application sets the service to running state. Note that this
92 * function enables the service to run - while the 'component' version
93 * of this function (as above) marks the service itself as ready */
94 ret = rte_service_runstate_set(id, 1);
97 Controlling A Service Core
98 ~~~~~~~~~~~~~~~~~~~~~~~~~~
100 This section demonstrates how to add a service core. The ``rte_service.h``
101 header file provides the functions for dynamically adding and removing cores.
102 The APIs to add and remove cores use lcore IDs similar to existing DPDK
105 These are the functions to start a service core, and have it run a service:
109 /* the lcore ID to use as a service core */
110 uint32_t service_core_id = 7;
111 ret = rte_service_lcore_add(service_core_id);
115 /* service cores are in "stopped" state when added, so start it */
116 ret = rte_service_lcore_start(service_core_id);
120 /* map a service to the service core, causing it to run the service */
121 uint32_t service_id; /* ID of a registered service */
122 uint32_t enable = 1; /* 1 maps the service, 0 unmaps */
123 ret = rte_service_map_lcore_set(service_id, service_core_id, enable);
128 Removing A Service Core
129 ~~~~~~~~~~~~~~~~~~~~~~~
131 To remove a service core, the steps are similar to adding but in reverse order.
132 Note that it is not allowed to remove a service core if the service is running,
133 and the service-core is the only core running that service (see documentation
134 for ``rte_service_lcore_stop`` function for details).
140 The service cores infrastructure provides DPDK with two main features. The first
141 is to abstract away hardware differences: the service core can CPU cycles to
142 a software fallback implementation, allowing the application to be abstracted
143 from the difference in HW / SW availability. The second feature is a flexible
144 method of registering functions to be run, allowing the running of the
145 functions to be scaled across multiple CPUs.