fc49ed25f1
Fix trivial typo (an -> and) in description of service core masks. Signed-off-by: Roy Franz <roy.franz@cavium.com> Acked-by: John McNamara <john.mcnamara@intel.com>
82 lines
3.9 KiB
ReStructuredText
82 lines
3.9 KiB
ReStructuredText
.. BSD LICENSE
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Copyright(c) 2017 Intel Corporation. All rights reserved.
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of Intel Corporation nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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Service Cores
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=============
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DPDK has a concept known as service cores, which enables a dynamic way of
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performing work on DPDK lcores. Service core support is built into the EAL, and
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an API is provided to optionally allow applications to control how the service
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cores are used at runtime.
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The service cores concept is built up out of services (components of DPDK that
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require CPU cycles to operate) and service cores (DPDK lcores, tasked with
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running services). The power of the service core concept is that the mapping
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between service cores and services can be configured to abstract away the
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difference between platforms and environments.
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For example, the Eventdev has hardware and software PMDs. Of these the software
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PMD requires an lcore to perform the scheduling operations, while the hardware
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PMD does not. With service cores, the application would not directly notice
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that the scheduling is done in software.
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For detailed information about the service core API, please refer to the docs.
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Service Core Initialization
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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There are two methods to having service cores in a DPDK application, either by
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using the service coremask, or by dynamically adding cores using the API.
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The simpler of the two is to pass the `-s` coremask argument to EAL, which will
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take any cores available in the main DPDK coremask, and if the bits are also set
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in the service coremask the cores become service-cores instead of DPDK
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application lcores.
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Enabling Services on Cores
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Each registered service can be individually mapped to a service core, or set of
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service cores. Enabling a service on a particular core means that the lcore in
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question will run the service. Disabling that core on the service stops the
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lcore in question from running the service.
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Using this method, it is possible to assign specific workloads to each
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service core, and map N workloads to M number of service cores. Each service
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lcore loops over the services that are enabled for that core, and invokes the
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function to run the service.
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Service Core Statistics
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~~~~~~~~~~~~~~~~~~~~~~~
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The service core library is capable of collecting runtime statistics like number
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of calls to a specific service, and number of cycles used by the service. The
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cycle count collection is dynamically configurable, allowing any application to
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profile the services running on the system at any time.
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