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author | 2017-03-28 11:34:11 +0530 | |
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committer | 2017-03-28 11:35:49 +0530 | |
commit | f1f3cc27f23bdde81c37d8142d4288d811bd5e45 (patch) | |
tree | 28aeabc93b7aed199fc123738d65d8f390a19a86 /docs/userguide/Ftrace.debugging.tool.userguide.rst | |
parent | 1f4ef5ee33f715c03a85a868f12e89744f889cff (diff) |
Update documentation structure.
This patch is used to update documentation structure.
Change-Id: I50d4ef4256ccfc57a0434123e7532a50000582cf
Co-Authored by:Srinivas <srinivas.atmakuri@tcs.com>
Co-Authored by:RajithaY<rajithax.yerrumsetty@intel.com>
Co-Authored by:shravani paladugula <shravanix.paladugula@intel.com>
Co-Authored by:Navya Bathula <navyax.bathula@intel.com>
Signed-off-by: Gundarapu Kalyan Reddy <reddyx.gundarapu@intel.com>
Diffstat (limited to 'docs/userguide/Ftrace.debugging.tool.userguide.rst')
-rw-r--r-- | docs/userguide/Ftrace.debugging.tool.userguide.rst | 259 |
1 files changed, 0 insertions, 259 deletions
diff --git a/docs/userguide/Ftrace.debugging.tool.userguide.rst b/docs/userguide/Ftrace.debugging.tool.userguide.rst deleted file mode 100644 index 95b7f8fe5..000000000 --- a/docs/userguide/Ftrace.debugging.tool.userguide.rst +++ /dev/null @@ -1,259 +0,0 @@ -.. This work is licensed under a Creative Commons Attribution 4.0 International License. - -.. http://creativecommons.org/licenses/by/4.0 - -===================== -FTrace Debugging Tool -===================== - -About Ftrace -------------- -Ftrace is an internal tracer designed to find what is going on inside the kernel. It can be used -for debugging or analyzing latencies and performance related issues that take place outside of -user-space. Although ftrace is typically considered the function tracer, it is really a frame -work of several assorted tracing utilities. - - One of the most common uses of ftrace is the event tracing. - -**Note:** -- For KVM4NFV, Ftrace is preferred as it is in-built kernel tool -- More stable compared to other debugging tools - -Version Features ----------------- - -+-----------------------------+-----------------------------------------------+ -| | | -| **Release** | **Features** | -| | | -+=============================+===============================================+ -| | - Ftrace Debugging tool is not implemented in | -| Colorado | Colorado release of KVM4NFV | -| | | -+-----------------------------+-----------------------------------------------+ -| | - Ftrace aids in debugging the KVM4NFV | -| Danube | 4.4-linux-kernel level issues | -| | - Option to disable if not required | -+-----------------------------+-----------------------------------------------+ - - -Implementation of Ftrace -------------------------- -Ftrace uses the debugfs file system to hold the control files as -well as the files to display output. - -When debugfs is configured into the kernel (which selecting any ftrace -option will do) the directory /sys/kernel/debug will be created. To mount -this directory, you can add to your /etc/fstab file: - -.. code:: bash - - debugfs /sys/kernel/debug debugfs defaults 0 0 - -Or you can mount it at run time with: - -.. code:: bash - - mount -t debugfs nodev /sys/kernel/debug - -Some configurations for Ftrace are used for other purposes, like finding latency or analyzing the system. For the purpose of debugging, the kernel configuration parameters that should be enabled are: - -.. code:: bash - - CONFIG_FUNCTION_TRACER=y - CONFIG_FUNCTION_GRAPH_TRACER=y - CONFIG_STACK_TRACER=y - CONFIG_DYNAMIC_FTRACE=y - -The above parameters must be enabled in /boot/config-4.4.0-el7.x86_64 i.e., kernel config file for ftrace to work. If not enabled, change the parameter to ``y`` and run., - -.. code:: bash - - On CentOS - grub2-mkconfig -o /boot/grub2/grub.cfg - sudo reboot - -Re-check the parameters after reboot before running ftrace. - -Files in Ftrace: ----------------- -The below is a list of few major files in Ftrace. - - ``current_tracer:`` - - This is used to set or display the current tracer that is configured. - - ``available_tracers:`` - - This holds the different types of tracers that have been compiled into the kernel. The tracers listed here can be configured by echoing their name into current_tracer. - - ``tracing_on:`` - - This sets or displays whether writing to the tracering buffer is enabled. Echo 0 into this file to disable the tracer or 1 to enable it. - - ``trace:`` - - This file holds the output of the trace in a human readable format. - - ``tracing_cpumask:`` - - This is a mask that lets the user only trace on specified CPUs. The format is a hex string representing the CPUs. - - ``events:`` - - It holds event tracepoints (also known as static tracepoints) that have been compiled into the kernel. It shows what event tracepoints exist and how they are grouped by system. - - -Avaliable Tracers ------------------ - -Here is the list of current tracers that may be configured based on usage. - -- function -- function_graph -- irqsoff -- preemptoff -- preemptirqsoff -- wakeup -- wakeup_rt - -Brief about a few: - - ``function:`` - - Function call tracer to trace all kernel functions. - - ``function_graph:`` - - Similar to the function tracer except that the function tracer probes the functions on their entry whereas the function graph tracer traces on both entry and exit of the functions. - - ``nop:`` - - This is the "trace nothing" tracer. To remove tracers from tracing simply echo "nop" into current_tracer. - -Examples: - -.. code:: bash - - - To list available tracers: - [tracing]# cat available_tracers - function_graph function wakeup wakeup_rt preemptoff irqsoff preemptirqsoff nop - - Usage: - [tracing]# echo function > current_tracer - [tracing]# cat current_tracer - function - - To view output: - [tracing]# cat trace | head -10 - - To Stop tracing: - [tracing]# echo 0 > tracing_on - - To Start/restart tracing: - [tracing]# echo 1 > tracing_on; - - -Ftrace in KVM4NFV ------------------ -Ftrace is part of KVM4NFV D-Release. KVM4NFV built 4.4-linux-Kernel will be tested by -executing cyclictest and analyzing the results/latency values (max, min, avg) generated. -Ftrace (or) function tracer is a stable kernel inbuilt debugging tool which tests real time -kernel and outputs a log as part of the code. These output logs are useful in following ways. - - - Kernel Debugging. - - Helps in Kernel code optimization and - - Can be used to better understand the kernel level code flow - -Ftrace logs for KVM4NFV can be found `here`_: - - -.. _here: http://artifacts.opnfv.org/kvmfornfv.html - -Ftrace Usage in KVM4NFV Kernel Debugging: ------------------------------------------ -Kvm4nfv has two scripts in /ci/envs to provide ftrace tool: - - - enable_trace.sh - - disable_trace.sh - -.. code:: bash - - Found at., - $ cd kvmfornfv/ci/envs - -Enabling Ftrace in KVM4NFV --------------------------- - -The enable_trace.sh script is triggered by changing ftrace_enable value in test_kvmfornfv.sh -script to 1 (which is zero by default). Change as below to enable Ftrace. - -.. code:: bash - - ftrace_enable=1 - -Note: - -- Ftrace is enabled before - -Details of enable_trace script ------------------------------- - -- CPU coremask is calculated using getcpumask() -- All the required events are enabled by, - echoing "1" to $TRACEDIR/events/event_name/enable file - -Example, - -.. code:: bash - - $TRACEDIR = /sys/kernel/debug/tracing/ - sudo bash -c "echo 1 > $TRACEDIR/events/irq/enable" - sudo bash -c "echo 1 > $TRACEDIR/events/task/enable" - sudo bash -c "echo 1 > $TRACEDIR/events/syscalls/enable" - -The set_event file contains all the enabled events list - -- Function tracer is selected. May be changed to other avaliable tracers based on requirement - -.. code:: bash - - sudo bash -c "echo function > $TRACEDIR/current_tracer - -- When tracing is turned ON by setting ``tracing_on=1``, the ``trace`` file keeps getting append with the traced data until ``tracing_on=0`` and then ftrace_buffer gets cleared. - -.. code:: bash - - To Stop/Pause, - echo 0 >tracing_on; - - To Start/Restart, - echo 1 >tracing_on; - -- Once tracing is diabled, disable_trace.sh script is triggered. - -Details of disable_trace Script -------------------------------- -In disable trace script the following are done: - -- The trace file is copied and moved to /tmp folder based on timestamp -- The current tracer file is set to ``nop`` -- The set_event file is cleared i.e., all the enabled events are disabled -- Kernel Ftrace is disabled/unmounted - - -Publishing Ftrace logs: ------------------------ -The generated trace log is pushed to `artifacts`_ by kvmfornfv-upload-artifact.sh -script available in releng which will be triggered as a part of kvm4nfv daily job. -The `trigger`_ in the script is., - -.. code:: bash - - echo "Uploading artifacts for future debugging needs...." - gsutil cp -r $WORKSPACE/build_output/log-*.tar.gz $GS_LOG_LOCATION > $WORKSPACE/gsutil.log 2>&1 - -.. _artifacts: https://artifacts.opnfv.org/ - -.. _trigger: https://gerrit.opnfv.org/gerrit/gitweb?p=releng.git;a=blob;f=jjb/kvmfornfv/kvmfornfv-upload-artifact.sh;h=56fb4f9c18a83c689a916dc6c85f9e3ddf2479b2;hb=HEAD#l53 |