Monday, 15 May 2017

Firmware Test Suite Text Based Front-End

The Firmware Test Suite (FWTS) has an easy to use text based front-end that is primarily used by the FWTS Live-CD image but it can also be used in the Ubuntu terminal.

To install and run the front-end use:

 sudo apt-get install fwts-frontend  
 sudo fwts-frontend-text  

..and one should see a menu of options:

In this demonstration, the "All Batch Tests" option has been selected:

Tests will be run one by one and a progress bar shows the progress of each test. Some tests run very quickly, others can take several minutes depending on the hardware configuration (such as number of processors).

Once the tests are all complete, the following dialogue box is displayed:

The test has saved several files into the directory /fwts/15052017/1748/ and selecting Yes one can view the results log in a scroll-box:

Exiting this, the FWTS frontend dialog is displayed:

Press enter to exit (note that the Poweroff option is just for the fwts Live-CD image version of fwts-frontend).

The tool dumps various logs, for example, the above run generated:

 ls -alt /fwts/15052017/1748/  
 total 1388  
 drwxr-xr-x 5 root root  4096 May 15 18:09 ..  
 drwxr-xr-x 2 root root  4096 May 15 17:49 .  
 -rw-r--r-- 1 root root 358666 May 15 17:49 acpidump.log  
 -rw-r--r-- 1 root root  3808 May 15 17:49 cpuinfo.log  
 -rw-r--r-- 1 root root 22238 May 15 17:49 lspci.log  
 -rw-r--r-- 1 root root 19136 May 15 17:49 dmidecode.log  
 -rw-r--r-- 1 root root 79323 May 15 17:49 dmesg.log  
 -rw-r--r-- 1 root root  311 May 15 17:49 README.txt  
 -rw-r--r-- 1 root root 631370 May 15 17:49 results.html  
 -rw-r--r-- 1 root root 281371 May 15 17:49 results.log  

acpidump.log is a dump of the ACPI tables in format compatible with the ACPICA acpidump tool.  The results.log file is a copy of the results generated by FWTS and results.html is a HTML formatted version of the log.

Monday, 8 May 2017

Simple job scripting in stress-ng 0.08.00

The latest release of stress-ng 0.08.00 now contains a new job scripting feature. Jobs allow one to bundle up a set of stress options  into a script rather than cram them all onto the command line.  One can now also run multiple invocations of a stressor with the latest version of stress-ng and conbined with job scripts we now have a powerful way of running more complex stress tests.

The job script commands are essentially the stress-ng long options without the need for the '--' option characters.  One option per line is allowed.

For example:

 $ stress-ng --cpu 1 --matrix 1 --verbose --tz --timeout 60s --cpu 1 --matrix -1 --icache 1 

would become:

 $cat example.job  
 timeout 60  
 cpu 1  
 matrix 1  
 icache 1  

One can also add comments using the # character prefix.   By default the stressors will be run in parallel, but one can use the "run sequential" command in the job script to run the stressors sequentially.

The following script runs the mmap stressor multiple times using more memory on each run:

 $ cat mmap.job  
 run sequential # one job at a time  
 timeout 2m   # run for 2 minutes  
 verbose     # verbose output  
 # run 4 invocations and increase memory each time  
 mmap 1  
 mmap-bytes 25%  
 mmap 1  
 mmap-bytes 50%  
 mmap 1  
 mmap-bytes 75%  
 mmap 1  
 mmap-bytes 100%  

Some of the stress-ng stressors have various "methods" that allow one to modify the way the stressor behaves.  The following example shows how job scripts can be uses to exercise a system using different stressor methods:

 $ cat /usr/share/stress-ng/example-jobs/matrix-methods.job   
 # hot-cpu class stressors:  
 #  various options have been commented out, one can remove the  
 #  proceeding comment to enable these options if required.  
 # run the following tests in parallel or sequentially  
 run sequential  
 # run parallel  
 # verbose  
 #  show all debug, warnings and normal information output.  
 # run each of the tests for 60 seconds  
 # stop stress test after N seconds. One can also specify the units  
 # of time in seconds, minutes, hours, days or years with the suf‐  
 # fix s, m, h, d or y.  
 timeout 1m  
 # tz  
 #  collect temperatures from the available thermal zones on the  
 #  machine (Linux only). Some devices may have one or more thermal  
 #  zones, where as others may have none.  
 # matrix stressor with examples of all the methods allowed  
 #  start N workers that perform various matrix operations on float‐  
 #  ing point values. By default, this will exercise all the matrix  
 #  stress methods one by one. One can specify a specific matrix  
 #  stress method with the --matrix-method option.  
 # Method      Description  
 # all       iterate over all the below matrix stress methods  
 # add       add two N × N matrices  
 # copy       copy one N × N matrix to another  
 # div       divide an N × N matrix by a scalar  
 # hadamard     Hadamard product of two N × N matrices  
 # frobenius    Frobenius product of two N × N matrices  
 # mean       arithmetic mean of two N × N matrices  
 # mult       multiply an N × N matrix by a scalar  
 # prod       product of two N × N matrices  
 # sub       subtract one N × N matrix from another N × N matrix  
 # trans      transpose an N × N matrix  
 matrix 0  
 matrix-method all  
 matrix 0  
 matrix-method add  
 matrix 0  
 matrix-method copy  
 matrix 0  
 matrix-method div  
 matrix 0  
 matrix-method frobenius  
 matrix 0  
 matrix-method hadamard  
 matrix 0  
 matrix-method mean  
 matrix 0  
 matrix-method mult  
 matrix 0  
 matrix-method prod  
 matrix 0  
 matrix-method sub  
 matrix 0  
 matrix-method trans  

Various example job scripts can be found in /usr/share/stress-ng/example-job, one can use these as a base for writing more complex stressors.  The example jobs have all the options commented (using the text from the stress-ng manual) to make it easier to see how each stressor can be run.

Version 0.08.00 landed in Ubuntu 17.10 Artful Aardvark and is available as a snap and I've got backports in ppa:colin-king/white for older releases of Ubuntu.

Thursday, 20 April 2017

Tracking CoverityScan issues on Linux-next

Over the past 6 months I've been running static analysis on linux-next with CoverityScan on a regular basis (to find new issues and fix some of them) as well as keeping a record of the defect count.

Since the beginning of September over 2000 defects have been eliminated by a host of upstream developers and the steady downward trend of outstanding issues is good to see.  A proportion of the outstanding defects are false positives or issues where the code is being overly zealous, for example, bounds checking where some conditions can never happen. Considering there are millions of lines of code, the defect rate is about average for such a large project.

I plan to keep the static analysis running long term and I'll try and post stats every 6 months or so to see how things are progressing.

Thursday, 5 January 2017

BCC: a powerful front end to extended Berkeley Packet Filters

The BPF Compiler Collection (BCC) is a toolkit for building kernel tracing tools that leverage the functionality provided by the Linux extended Berkeley Packet Filters (BPF).

BCC allows one to write BPF programs with front-ends in Python or Lua with kernel instrumentation written in C.  The instrumentation code is built into sandboxed eBPF byte code and is executed in the kernel.

The BCC github project README file provides an excellent overview and description of BCC and the various available BCC tools.  Building BCC from scratch can be a bit time consuming, however,  the good news is that the BCC tools are now available as a snap and so BCC can be quickly and easily installed just using:

 sudo snap install --devmode bcc  

There are currently over 50 BCC tools in the snap, so let's have a quick look at a few:

cachetop allows one to view the top page cache hit/miss statistics. To run this use:

 sudo bcc.cachetop  

The funccount tool allows one to count the number of times specific functions get called.  For example, to see how many kernel functions with the name starting with "do_" get called per second one can use:

 sudo bcc.funccount "do_*" -i 1  

To see how to use all the options in this tool, use the -h option:

 sudo bcc.funccount -h  

I've found the funccount tool to be especially useful to check on kernel activity by checking on hits on specific function names.

The slabratetop tool is useful to see the active kernel SLAB/SLUB memory allocation rates:

 sudo bcc.slabratetop  

If you want to see which process is opening specific files, one can snoop on open system calls use the opensnoop tool:

 sudo bcc.opensnoop -T

Hopefully this will give you a taste of the useful tools that are available in BCC (I have barely scratched the surface in this article).  I recommend installing the snap and giving it a try.

As it stands,BCC provides a useful mechanism to develop BPF tracing tools and I look forward to regularly updating the BCC snap as more tools are added to BCC. Kudos to Brendan Gregg for BCC!