Hackfest1403-2

Hackfest March 2014 at Ettus Research

Nathan West: Perf Counters and Monitor Enhancements

• Added new performance counters
  • CPU cycles
  • branch instructions
  • branch misses
  • cache references
• Uses same interface as used by perf; built in support to Performance Counters
• Updated the gr-perf-monitorx:
  • Can select which perf counter the block size is based on (currently, only reps work time counter)
  • Tooltip popup for each block to show all PCs

Example:

WIP: https://github.com/n-west/gnuradio/tree/linux-perf-counters

Todo:

• Make platform independent (ifdef out for OSX and Windows for now)
• Make sure we know the kernel requirements; check for them
• Test on ARM and any other platforms we can
• Add percent of total to tooltip popup

By GRCon14, have some success case and walk-through on how to use them. Take a block and get performance counter info; identify the areas that need work, fix them, and show that that changes the counters.

Tom Rondeau and Nick McCarthy

• Focused on integrating fecapi from https://github.com/namccart/fecapi into GNU Radio as part of gr-fec.
• Allows us to use an "encoder" and "decoder" block in a flowgraph.
  • encoding and decoding for specific codes are passed as objects to these blocks
  • GR blocks take care of things related to codes but not specific to any specific code
    • puncturing
    • threading models: 'capillary' is the default as a way to branch the threading model
• We have convolutional codes (rate=2, K=7) working
• Working on getting LDPC working from last GSoC as FECAPI-compatible
  • Been in touch with Manu and Tracie to see about competing this
• Shown the CC working with a GNU Radio modem over a simulated channel
• Future Work
  • Near term:
    • Wrap up work done to integrate FECAPI; fix up some of the function calls
    • DOCUMENTATION
    • Clean up new work done to make detection and soft decision modems work with FEC blocks
  • Longer term:
    • More codes: Reed-Solomon as outer code; LDPC; others
    • Ability to adjust codes are runtime

Nick Foster

• Improving MSK handling
• MSK correlator block for burst sync
  • extension of correlate_and_sync for MSK (with Gaussian filter)
    • Set BT=5 (i.e., some large number) for MSK
• New MSK timing synchronization block
• HDLC framer and deframer
  • already issued a pull request (172

Tom Tsou (not GNU Radio specific)

• Showed an LTE 20 MHZ signal receiver
• Showed timing recovery with Zadoff-Chu
  • sub-banded to ~1 Msps
• Showed off his 3GPP approved "butterfly" channel model
  • two antennas connected to a USRP moved up-and-down rapidly
• Also used handcar model
  • USRP on a cart pushed back and forth
• QAM64 received signal in realtime

Ben Reynwar

• hierblocks for PFB channelizers (for threading control)
  • pull request 180
• working on synthesizers
• want: hier block for building reconstruction filters
  • Develop a model to autobuild a channelizer for for different channels and channel sizes
  • Related to Tom Rondeau's recent paper
  • The main trick will be in defining the channel structure

John Malsbury and Balint Seeber

• worked on gr-mac (formerly gr-precog migrated to 3.7)
• Support for:
  • ARQ
  • fragmenting
  • ARP
  • TUN/TAP or raw socket interface
  • Passing PDUs to higher layers
• Showed OTA
  • played BZTank (or BZFlag) over GR link
• Balint issued a number of pull request patches to improve GR's support for gr-mac

Here's Balint and John showing off their work.

Philip Balister

• Improving OpenEmbedded support for GNU Radio
  • fixed issue with missing libgnuradio-xxx.so (without version)
  • almost fixed swig2.0 (CMake looks for swig2.0 before swig; confusing things)
• This work will allow us to use the SDK to build both GNU Radio and GR OOT projects

Michael Dickens

• OSX cpu-thread affinity work:
  • Determined that OSX kernel (mach / darwin), while providing an API for thread-cpu affinity, really-truly does not actually implement the functionality for doing so;
  • The provided API functions are "processor_set_create" and "processor_set_destroy" from processor.c, and "thread_assign" from thread.c;
  • There is one "CPU set" (global "pset0" from processor.c) which contains all active processors;
  • Threads are assigned to active processors in the global CPU set as determined by the selected scheduling protocol (e.g., FIFO, RR) only;
  • User (even as sudo) has no control over thread-cpu assignments;
  • Work abandoned; no need to address this issue again! !@#% Apple ...

• 3 pull requests to GR maint, with 5 fixes including ticket #660

• Started addressing the "two-clock" problem:
  • See, e.g., this thread on the GR discussion list
  • When more than 1 sink/source is sample-rate based (e.g., audio source -> uhd sink);
  • Actual sample rates will generally be close to those specified, but can easily be different by an unknown amount;
  • When the sample rates differ, the flow graph will either eventually starve (sink is going faster than source), or back-pressure (source is going faster than sink);
  • Proposed solution:
    • Embed an arbitrary resampler to adjust the rates of a hardware source/sink once data is in the SDR flow-graph, or, if possible, using the hardware itself (e.g., OSX audio can do this easily);
    • 1 input, 1 output; watch buffer "fullness" and try to keep within "reasonable" bounds (e.g., 25% to 75% full);
    • Would be completely optional, disabled by default, enabled by user preference variable (name is to be decided);
    • Implemented as a block inserted automatically between hardware source/sink and the next block, 1 input / 1 output;
    • Inserted in flat_flowgraph or block_executor;
    • Work in progress.

Tim O'Shea

• Focused on understanding the differences and uses of tagged stream blocks versus/with message PDUs
• Performance measurement and comparisons of equivalent tagged stream blocks and message blocks https://github.com/osh/gr-chunky
• Fix pmt's to_python and from_python methods for numpy arrays and uniform vectors for all supported types
• Looking into problem of flow control in message passing system
• Borrowed Phil's ODroid XU to add Arm-A15 benchmarks to http://stats.gnuradio.org/
• Worked on improved TDMA burst modem capabilities along with updated message-enabled eventstream blocks
• Built and posted a set of fpdu and cpdu plotting message blocks to be used in QT Guis https://github.com/osh/gr-pyqt