[dpdk-dev,v2] doc: arm64: document DPDK application profiling methods

Message ID 1475657009-11139-1-git-send-email-jerin.jacob@caviumnetworks.com
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show

Commit Message

Jerin Jacob Oct. 5, 2016, 8:43 a.m.
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

Thomas Monjalon Oct. 26, 2016, 8:07 p.m. | #1
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
Mcnamara, John Nov. 3, 2016, 12:30 p.m. | #2
> -----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.
Mcnamara, John Nov. 4, 2016, 2 p.m. | #3
> -----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

Patch

diff --git a/doc/guides/prog_guide/profile_app.rst b/doc/guides/prog_guide/profile_app.rst
index 3226187..9f1b7ee 100644
--- a/doc/guides/prog_guide/profile_app.rst
+++ b/doc/guides/prog_guide/profile_app.rst
@@ -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.