61. Profile Your Application

The following sections describe methods of profiling DPDK applications on different architectures.

61.1. Profiling on x86

Intel processors provide performance counters to monitor events. Some tools provided by Intel, such as Intel® VTune™ Amplifier, can be used to profile and benchmark an application. See the VTune Performance Analyzer Essentials publication from Intel Press for more information.

For a DPDK application, this can be done in a Linux* application environment only.

The main situations that should be monitored through event counters are:

  • Cache misses
  • Branch mis-predicts
  • DTLB misses
  • Long latency instructions and exceptions

Refer to the Intel Performance Analysis Guide for details about application profiling.

61.1.1. Profiling with VTune

To allow VTune attaching to the DPDK application, reconfigure and recompile the DPDK with CONFIG_RTE_ETHDEV_RXTX_CALLBACKS and CONFIG_RTE_ETHDEV_PROFILE_WITH_VTUNE enabled.

61.2. Profiling on ARM64

61.2.1. Using Linux perf

The ARM64 architecture provide performance counters to monitor events. The Linux perf tool can be used to profile and benchmark an application. In addition to the standard events, perf can be used to profile arm64 specific PMU (Performance Monitor Unit) events through raw events (-e -rXX).

For more derails refer to the ARM64 specific PMU events enumeration.

61.2.2. High-resolution cycle counter

The default cntvct_el0 based rte_rdtsc() provides a portable means to get a wall clock counter in user space. Typically it runs at <= 100MHz.

The alternative method to enable rte_rdtsc() for a high resolution wall clock counter is through the ARMv8 PMU subsystem. The PMU cycle counter runs at CPU frequency. However, access to the PMU cycle counter from user space is not enabled by default in the arm64 linux kernel. It is possible to enable cycle counter for user space access by configuring the PMU from the privileged mode (kernel space).

By default the rte_rdtsc() implementation uses a portable cntvct_el0 scheme. Application can choose the PMU based implementation with CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU.

The example below shows the steps to configure the PMU based cycle counter on an ARMv8 machine.

git clone https://github.com/jerinjacobk/armv8_pmu_cycle_counter_el0
cd armv8_pmu_cycle_counter_el0
make
sudo insmod pmu_el0_cycle_counter.ko
cd $DPDK_DIR
make config T=arm64-armv8a-linux-gcc
echo "CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU=y" >> build/.config
make

Warning

The PMU based scheme is useful for high accuracy performance profiling with rte_rdtsc(). However, this method can not be used in conjunction with Linux userspace profiling tools like perf as this scheme alters the PMU registers state.