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Posts tagged with 'benchmarking'

Colin Ian King

Intel rdrand instruction revisited

A few months ago I did a quick and dirty benchmark of the Intel rdrand instruction found on the new Ivybridge processors.  I did some further analysis a while ago and I've only just got around to writing up my findings. I've improved the test by exercising the Intel Digital Random Number Generator (DRNG) with multiple threads and also re-writing the rdrand wrapper in assembler and ensuring the code is inline'd.  The source code for this test is available here.

So, how does it shape up?  On a i5-3210M (2.5GHz) Ivybridge (2 cores, 4 threads) I get a peak of ~99.6 million 64 bit rdrands per second with 4 threads which equates to ~6.374 billion bits per second.  Not bad at all.

With a 4 threaded i5-3210M CPU we hit maximum rdrand throughput with 4 threads.

..and with a 8 threaded i7-3770 (3.4GHz) Ivybridge (4 cores, 8 threads) we again hit a peak throughput of 99.6 million 64 bit rdrands a second on 3 threads. One can therefore conclude that this is the peak rate of the DNRG on both CPUs tested.  A 2 threaded i3 Ivybridge CPU won't be able to hit the peak rate of the DNRG, and a 4 threaded i5 can only just max out the DNRG with some hand-optimized code.

Now how random is this random data?  There are several tests available; I chose to exercise the DRNG using the dieharder test suite.  The test is relatively simple; install dieharder and do 64 bit rdrand reads and output these as a raw random number stream and pipe this into dieharder:

 sudo apt-get install dieharder  
./rdrand-test | dieharder -g 200 -a
# dieharder version 3.31.1 Copyright 2003 Robert G. Brown #
rng_name |rands/second| Seed |
stdin_input_raw| 3.66e+07 | 639263374|
test_name |ntup| tsamples |psamples| p-value |Assessment
diehard_birthdays| 0| 100| 100|0.40629140| PASSED
diehard_operm5| 0| 1000000| 100|0.79942347| PASSED
diehard_rank_32x32| 0| 40000| 100|0.35142889| PASSED
diehard_rank_6x8| 0| 100000| 100|0.75739694| PASSED
diehard_bitstream| 0| 2097152| 100|0.65986567| PASSED
diehard_opso| 0| 2097152| 100|0.24791918| PASSED
diehard_oqso| 0| 2097152| 100|0.36850828| PASSED
diehard_dna| 0| 2097152| 100|0.52727856| PASSED
diehard_count_1s_str| 0| 256000| 100|0.08299753| PASSED
diehard_count_1s_byt| 0| 256000| 100|0.31139908| PASSED
diehard_parking_lot| 0| 12000| 100|0.47786440| PASSED
diehard_2dsphere| 2| 8000| 100|0.93639860| PASSED
diehard_3dsphere| 3| 4000| 100|0.43241488| PASSED
diehard_squeeze| 0| 100000| 100|0.99088862| PASSED
diehard_sums| 0| 100| 100|0.00422846| WEAK
diehard_runs| 0| 100000| 100|0.48432365| PASSED
dab_monobit2| 12| 65000000| 1|0.98439048| PASSED

..and leave to cook for about 45 minutes.  The -g 200 option specifies that the random numbers come from stdin and the -a option runs all the dieharder tests.  All the tests passed with the exception of the diehard_sums test which produced "weak" results, however, this test is known to be unreliable and recommended not to be used.  Quite honestly, I would be surprised if the tests failed, but you never know until one runs them.

The CA cert research labs have an on-line random number generator analysis website allowing one to submit and test at least 12 MB of random numbers. I submitted 32 MB of data, and I am currently waiting to see if I get any results back.  Watch this space.

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Colin Ian King

Previously I blogged about blktrace and how it can be used to analyse block I/O operations - however, it can generate a lot of data that can be overwhelming. This is where Chris Mason's Seekwatcher tool comes to the rescue. Seekwatcher uses blktrace data to generate graphs to help one visualise and understand I/O patterns. It allows one to plot multiple blktrace runs together to enable easy comparison between benchmarking test runs.

It requires matplotlib, python and the numpy module - on Ubuntu download and install these packages using:

sudo apt-get install python python-matplotlib python-numpy

and then get the seekwatcher source and extract seekwatcher from the source package and you are ready to run the seekwatcher python script.

Seekwatcher also can general animations of I/O patterns which also improves visualisation and understanding of I/O operations over time.

To use seekwacher, first start a blktrace capture:

blktrace -o trace -d /dev/sda

next kick off the test you want to analyse and when that's complete, kill blktrace. Next run seekwatcher on the blktrace output:

seekwatcher -t trace.blktrace -o output.png

..and this generates a png file output.png. Easy!

Attached is the output from a test I just ran on my HP Mini 1000 starting up the Open Office word processor:

One can generate a movie from the same data using:

seekwatcher -t trace.blktrace -o open-office.mpg --movie

The generated movie is below:

There are more instructions on other ways to use seekwatcher on the seekwatcher webpage. All in all, a very handy tool - kudos to Chris Mason.

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