d/numam-dpdk
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

doc: add ARM profiling methods

Browse Source 
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Signed-off-by: John McNamara <john.mcnamara@intel.com>
Acked-by: Jianbo Liu <jianbo.liu@linaro.org>
This commit is contained in:
Jerin Jacob 2016-11-08 09:02:56 +05:30 committed by Thomas Monjalon
parent 9a998f2dda
commit 9d5ba88c2d
1 changed files with 63 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
doc/guides/prog_guide/profile_app.rst
View File

@ -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.