X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;f=doc%2Fguides%2Fprog_guide%2Fpower_man.rst;h=0a3755a901758f08da8eedc1763177ceef005e5a;hb=cacf8267cc14e84384dbc86f24f6b10e8aedbcbc;hp=fdf8f5fddbe231237b7426105da91b3877e870b6;hpb=d9e71f5227c1ead88b703e6015ae0f3b9c83b5af;p=dpdk.git diff --git a/doc/guides/prog_guide/power_man.rst b/doc/guides/prog_guide/power_man.rst index fdf8f5fddb..0a3755a901 100644 --- a/doc/guides/prog_guide/power_man.rst +++ b/doc/guides/prog_guide/power_man.rst @@ -1,32 +1,5 @@ -.. BSD LICENSE - Copyright(c) 2010-2014 Intel Corporation. All rights reserved. - All rights reserved. - - Redistribution and use in source and binary forms, with or without - modification, are permitted provided that the following conditions - are met: - - * Redistributions of source code must retain the above copyright - notice, this list of conditions and the following disclaimer. - * Redistributions in binary form must reproduce the above copyright - notice, this list of conditions and the following disclaimer in - the documentation and/or other materials provided with the - distribution. - * Neither the name of Intel Corporation nor the names of its - contributors may be used to endorse or promote products derived - from this software without specific prior written permission. - - THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS - "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT - LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR - A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT - OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, - SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT - LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, - DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY - THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT - (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE - OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2010-2014 Intel Corporation. Power Management ================ @@ -133,9 +106,97 @@ User Cases The power management mechanism is used to save power when performing L3 forwarding. + +Empty Poll API +-------------- + +Abstract +~~~~~~~~ + +For packet processing workloads such as DPDK polling is continuous. +This means CPU cores always show 100% busy independent of how much work +those cores are doing. It is critical to accurately determine how busy +a core is hugely important for the following reasons: + + * No indication of overload conditions + * User does not know how much real load is on a system, resulting + in wasted energy as no power management is utilized + +Compared to the original l3fwd-power design, instead of going to sleep +after detecting an empty poll, the new mechanism just lowers the core frequency. +As a result, the application does not stop polling the device, which leads +to improved handling of bursts of traffic. + +When the system become busy, the empty poll mechanism can also increase the core +frequency (including turbo) to do best effort for intensive traffic. This gives +us more flexible and balanced traffic awareness over the standard l3fwd-power +application. + + +Proposed Solution +~~~~~~~~~~~~~~~~~ +The proposed solution focuses on how many times empty polls are executed. +The less the number of empty polls, means current core is busy with processing +workload, therefore, the higher frequency is needed. The high empty poll number +indicates the current core not doing any real work therefore, we can lower the +frequency to safe power. + +In the current implementation, each core has 1 empty-poll counter which assume +1 core is dedicated to 1 queue. This will need to be expanded in the future to +support multiple queues per core. + +Power state definition: +^^^^^^^^^^^^^^^^^^^^^^^ + +* LOW: Not currently used, reserved for future use. + +* MED: the frequency is used to process modest traffic workload. + +* HIGH: the frequency is used to process busy traffic workload. + +There are two phases to establish the power management system: +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +* Training phase. This phase is used to measure the optimal frequency + change thresholds for a given system. The thresholds will differ from + system to system due to differences in processor micro-architecture, + cache and device configurations. + In this phase, the user must ensure that no traffic can enter the + system so that counts can be measured for empty polls at low, medium + and high frequencies. Each frequency is measured for two seconds. + Once the training phase is complete, the threshold numbers are + displayed, and normal mode resumes, and traffic can be allowed into + the system. These threshold number can be used on the command line + when starting the application in normal mode to avoid re-training + every time. + +* Normal phase. Every 10ms the run-time counters are compared + to the supplied threshold values, and the decision will be made + whether to move to a different power state (by adjusting the + frequency). + +API Overview for Empty Poll Power Management +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +* **State Init**: initialize the power management system. + +* **State Free**: free the resource hold by power management system. + +* **Update Empty Poll Counter**: update the empty poll counter. + +* **Update Valid Poll Counter**: update the valid poll counter. + +* **Set the Frequency Index**: update the power state/frequency mapping. + +* **Detect empty poll state change**: empty poll state change detection algorithm then take action. + +User Cases +---------- +The mechanism can applied to any device which is based on polling. e.g. NIC, FPGA. + References ---------- -* l3fwd-power: The sample application in DPDK that performs L3 forwarding with power management. +* The :doc:`../sample_app_ug/l3_forward_power_man` + chapter in the :doc:`../sample_app_ug/index` section. -* The "L3 Forwarding with Power Management Sample Application" chapter in the *DPDK Sample Application's User Guide*. +* The :doc:`../sample_app_ug/vm_power_management` + chapter in the :doc:`../sample_app_ug/index` section.