1.. BSD LICENSE 2 Copyright(c) 2017 Intel Corporation. All rights reserved. 3 All rights reserved. 4 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions 7 are met: 8 9 * Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 * Redistributions in binary form must reproduce the above copyright 12 notice, this list of conditions and the following disclaimer in 13 the documentation and/or other materials provided with the 14 distribution. 15 * Neither the name of Intel Corporation nor the names of its 16 contributors may be used to endorse or promote products derived 17 from this software without specific prior written permission. 18 19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31Service Cores 32============= 33 34DPDK has a concept known as service cores, which enables a dynamic way of 35performing work on DPDK lcores. Service core support is built into the EAL, and 36an API is provided to optionally allow applications to control how the service 37cores are used at runtime. 38 39The service cores concept is built up out of services (components of DPDK that 40require CPU cycles to operate) and service cores (DPDK lcores, tasked with 41running services). The power of the service core concept is that the mapping 42between service cores and services can be configured to abstract away the 43difference between platforms and environments. 44 45For example, the Eventdev has hardware and software PMDs. Of these the software 46PMD requires an lcore to perform the scheduling operations, while the hardware 47PMD does not. With service cores, the application would not directly notice 48that the scheduling is done in software. 49 50For detailed information about the service core API, please refer to the docs. 51 52Service Core Initialization 53~~~~~~~~~~~~~~~~~~~~~~~~~~~ 54 55There are two methods to having service cores in a DPDK application, either by 56using the service coremask, or by dynamically adding cores using the API. 57The simpler of the two is to pass the `-s` coremask argument to EAL, which will 58take any cores available in the main DPDK coremask, and if the bits are also set 59in the service coremask the cores become service-cores instead of DPDK 60application lcores. 61 62Enabling Services on Cores 63~~~~~~~~~~~~~~~~~~~~~~~~~~ 64 65Each registered service can be individually mapped to a service core, or set of 66service cores. Enabling a service on a particular core means that the lcore in 67question will run the service. Disabling that core on the service stops the 68lcore in question from running the service. 69 70Using this method, it is possible to assign specific workloads to each 71service core, and map N workloads to M number of service cores. Each service 72lcore loops over the services that are enabled for that core, and invokes the 73function to run the service. 74 75Service Core Statistics 76~~~~~~~~~~~~~~~~~~~~~~~ 77 78The service core library is capable of collecting runtime statistics like number 79of calls to a specific service, and number of cycles used by the service. The 80cycle count collection is dynamically configurable, allowing any application to 81profile the services running on the system at any time. 82