1.. BSD LICENSE 2 Copyright(c) 2010-2014 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 31Profile Your Application 32======================== 33 34The following sections describe methods of profiling DPDK applications on 35different architectures. 36 37 38Profiling on x86 39---------------- 40 41Intel processors provide performance counters to monitor events. 42Some tools provided by Intel, such as Intel® VTune™ Amplifier, can be used 43to profile and benchmark an application. 44See the *VTune Performance Analyzer Essentials* publication from Intel Press for more information. 45 46For a DPDK application, this can be done in a Linux* application environment only. 47 48The main situations that should be monitored through event counters are: 49 50* Cache misses 51 52* Branch mis-predicts 53 54* DTLB misses 55 56* Long latency instructions and exceptions 57 58Refer to the 59`Intel Performance Analysis Guide <http://software.intel.com/sites/products/collateral/hpc/vtune/performance_analysis_guide.pdf>`_ 60for details about application profiling. 61 62 63Empty cycles tracing 64~~~~~~~~~~~~~~~~~~~~ 65 66Iterations that yielded no RX packets (empty cycles, wasted iterations) can 67be analyzed using VTune Amplifier. This profiling employs the 68`Instrumentation and Tracing Technology (ITT) API 69<https://software.intel.com/en-us/node/544195>`_ 70feature of VTune Amplifier and requires only reconfiguring the DPDK library, 71no changes in a DPDK application are needed. 72 73To trace wasted iterations on RX queues, first reconfigure DPDK with 74``CONFIG_RTE_ETHDEV_RXTX_CALLBACKS`` and 75``CONFIG_RTE_ETHDEV_PROFILE_ITT_WASTED_RX_ITERATIONS`` enabled. 76 77Then rebuild DPDK, specifying paths to the ITT header and library, which can 78be found in any VTune Amplifier distribution in the *include* and *lib* 79directories respectively: 80 81.. code-block:: console 82 83 make EXTRA_CFLAGS=-I<path to ittnotify.h> \ 84 EXTRA_LDLIBS="-L<path to libittnotify.a> -littnotify" 85 86Finally, to see wasted iterations in your performance analysis results, 87select the *"Analyze user tasks, events, and counters"* checkbox in the 88*"Analysis Type"* tab when configuring analysis via VTune Amplifier GUI. 89Alternatively, when running VTune Amplifier via command line, specify 90``-knob enable-user-tasks=true`` option. 91 92Collected regions of wasted iterations will be marked on VTune Amplifier's 93timeline as ITT tasks. These ITT tasks have predefined names, containing 94Ethernet device and RX queue identifiers. 95 96 97Profiling on ARM64 98------------------ 99 100Using Linux perf 101~~~~~~~~~~~~~~~~ 102 103The ARM64 architecture provide performance counters to monitor events. The 104Linux ``perf`` tool can be used to profile and benchmark an application. In 105addition to the standard events, ``perf`` can be used to profile arm64 106specific PMU (Performance Monitor Unit) events through raw events (``-e`` 107``-rXX``). 108 109For more derails refer to the 110`ARM64 specific PMU events enumeration <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.100095_0002_04_en/way1382543438508.html>`_. 111 112 113High-resolution cycle counter 114~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 115 116The default ``cntvct_el0`` based ``rte_rdtsc()`` provides a portable means to 117get a wall clock counter in user space. Typically it runs at <= 100MHz. 118 119The alternative method to enable ``rte_rdtsc()`` for a high resolution wall 120clock counter is through the armv8 PMU subsystem. The PMU cycle counter runs 121at CPU frequency. However, access to the PMU cycle counter from user space is 122not enabled by default in the arm64 linux kernel. It is possible to enable 123cycle counter for user space access by configuring the PMU from the privileged 124mode (kernel space). 125 126By default the ``rte_rdtsc()`` implementation uses a portable ``cntvct_el0`` 127scheme. Application can choose the PMU based implementation with 128``CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU``. 129 130The example below shows the steps to configure the PMU based cycle counter on 131an armv8 machine. 132 133.. code-block:: console 134 135 git clone https://github.com/jerinjacobk/armv8_pmu_cycle_counter_el0 136 cd armv8_pmu_cycle_counter_el0 137 make 138 sudo insmod pmu_el0_cycle_counter.ko 139 cd $DPDK_DIR 140 make config T=arm64-armv8a-linuxapp-gcc 141 echo "CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU=y" >> build/.config 142 make 143 144.. warning:: 145 146 The PMU based scheme is useful for high accuracy performance profiling with 147 ``rte_rdtsc()``. However, this method can not be used in conjunction with 148 Linux userspace profiling tools like ``perf`` as this scheme alters the PMU 149 registers state. 150