[dpdk-dev] doc: arm64: document DPDK application profiling methods
Commit Message
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---
doc/guides/prog_guide/profile_app.rst | 58 +++++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)
Comments
Thanks for providing a patch so quickly :)
2016-10-04 16:10, Jerin Jacob:
> +The PMU based scheme useful for high accuracy performance profiling.
A verb is missing.
> +Find below the example 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
What about the ARM 32 code that Jan is using?
> +.. warning::
> +
> + This method can not be used in production systems as this may alter PMU
> + state used by standard Linux user space tool like perf.
More details please?
On Tue, 04 Oct 2016 14:40:47 +0200
Thomas Monjalon <thomas.monjalon@6wind.com> wrote:
> Thanks for providing a patch so quickly :)
>
> 2016-10-04 16:10, Jerin Jacob:
> > +The PMU based scheme useful for high accuracy performance profiling.
>
> A verb is missing.
>
> > +Find below the example 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
>
> What about the ARM 32 code that Jan is using?
Hi, I didn't have time for this yet. The basic description is here:
lib/librte_eal/common/include/arch/arm/rte_cycles_32.h
In the Linux Kernel, it is used here:
arch/arm/kernel/perf_event_v7.c (see registers c12, c13 and c14)
Regards
Jan
>
> > +.. warning::
> > +
> > + This method can not be used in production systems as this may alter PMU
> > + state used by standard Linux user space tool like perf.
>
> More details please?
>
@@ -31,6 +31,14 @@
Profile Your Application
========================
+Introduction
+------------
+
+The following sections describe the methods to profile DPDK applications on
+different architectures.
+
+x86
+~~~
Intel processors provide performance counters to monitor events.
Some tools provided by Intel can be used to profile and benchmark an application.
See the *VTune Performance Analyzer Essentials* publication from Intel Press for more information.
@@ -50,3 +58,53 @@ 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.
+
+ARM64
+~~~~~
+
+Perf
+^^^^
+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 events through raw events(-e -rXX)
+
+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 portable means to get wall
+clock counter at user space. Typically it runs at <= 100MHz.
+
+The alternative method to enable rte_rdtsc() for high resolution
+wall clock counter is through armv8 PMU subsystem.
+The PMU cycle counter runs at CPU frequency, However, access to PMU cycle
+counter from user space is not enabled by default in the arm64 linux kernel.
+It is possible to enable cycle counter at user space access
+by configuring the PMU from the privileged mode (kernel space).
+
+by default rte_rdtsc() implementation uses portable cntvct_el0 scheme.
+Application can choose the PMU based implementation with
+CONFIG_RTE_ARM_EAL_RDTSC_USE_PMU
+
+The PMU based scheme useful for high accuracy performance profiling.
+Find below the example 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::
+
+ This method can not be used in production systems as this may alter PMU
+ state used by standard Linux user space tool like perf.
+