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Diffstat (limited to 'doc/guides/prog_guide/profile_app.rst')
| -rw-r--r-- | doc/guides/prog_guide/profile_app.rst | 64 |
1 files changed, 63 insertions, 1 deletions
diff --git a/doc/guides/prog_guide/profile_app.rst b/doc/guides/prog_guide/profile_app.rst index 32261875..54b546ac 100644 --- a/doc/guides/prog_guide/profile_app.rst +++ b/doc/guides/prog_guide/profile_app.rst @@ -31,8 +31,15 @@ Profile Your Application ======================== +The following sections describe methods of profiling DPDK applications on +different architectures. + + +Profiling on x86 +---------------- + Intel processors provide performance counters to monitor events. -Some tools provided by Intel can be used to profile and benchmark an application. +Some tools provided by Intel, such as VTune, 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. @@ -50,3 +57,58 @@ The main situations that should be monitored through event counters are: Refer to the `Intel Performance Analysis Guide <http://software.intel.com/sites/products/collateral/hpc/vtune/performance_analysis_guide.pdf>`_ for details about application profiling. + + +Profiling on ARM64 +------------------ + +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 <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.100095_0002_04_en/way1382543438508.html>`_. + + +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. + +.. code-block:: console + + 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-linuxapp-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. |