[dpdk-dev,v2] doc: arm64: document DPDK application profiling methods
Commit Message
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---
v2:
-Addressed ARM64 specific review comments(Suggested by Thomas)
http://dpdk.org/dev/patchwork/patch/16362/
---
doc/guides/prog_guide/profile_app.rst | 58 +++++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)
Comments
2016-10-05 14:13, Jerin Jacob:
> Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> ---
> v2:
> -Addressed ARM64 specific review comments(Suggested by Thomas)
I feel more comments could be done, especially about formatting.
You are adding a chapter Introduction without any other section
of the same level.
Some technical terms should be enclosed in backquotes.
Please John, could you guide Jerin or provide an updated version?
Thanks
> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Wednesday, October 26, 2016 9:07 PM
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>; Mcnamara, John
> <john.mcnamara@intel.com>
> Cc: dev@dpdk.org; jianbo.liu@linaro.org; viktorin@rehivetech.com
> Subject: Re: [dpdk-dev] [PATCH v2] doc: arm64: document DPDK application
> profiling methods
>
> 2016-10-05 14:13, Jerin Jacob:
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> > v2:
> > -Addressed ARM64 specific review comments(Suggested by Thomas)
>
> I feel more comments could be done, especially about formatting.
> You are adding a chapter Introduction without any other section of the
> same level.
> Some technical terms should be enclosed in backquotes.
>
> Please John, could you guide Jerin or provide an updated version?
Will do.
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jerin Jacob
> Sent: Wednesday, October 5, 2016 9:43 AM
> To: dev@dpdk.org
> Cc: thomas.monjalon@6wind.com; jianbo.liu@linaro.org;
> viktorin@rehivetech.com; Jerin Jacob <jerin.jacob@caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH v2] doc: arm64: document DPDK application
> profiling methods
>
Hi Jerin,
Thanks for this. It is probably something that should be extended from
the Intel side as well.
...
> Profile Your Application
> ========================
>
> +Introduction
> +------------
> +
> +The following sections describe the methods to profile DPDK
> +applications on different architectures.
You could probably just skip the introduction heading and put this
text under the main heading.
As Thomas pointed out there are a few other RST formatting issues
as well. I'll forward some suggested changes.
John
@@ -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
+
+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::
+
+ 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.