On Tue, 2015-06-16 at 12:01 -0400, discuss-gnuradio-requ...@gnu.org wrote: > From: Thanasis Balafoutis <abalafou...@gmail.com> > To: "discuss-gnuradio@gnu.org" <discuss-gnuradio@gnu.org> > Subject: [Discuss-gnuradio] CPU usage when hdlc framer is used
> Hi, > > CPU usage goes to 100% when the hdlc_framer block is used! > To verify this I did the following tests: > > 1. message_strobe_random ----> message_debug (CPU usage 2%) > 2. message_strobe_random ----> hdlc_framer----> null_sink (CPU usage 100%) > > Any idea how can I avoid this overload? Off the cuff, it appears the hdlc_framer needs at least one fix: 1. If oidx == 0, it should use a blocking fetch of a message here: https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/hdlc_framer_pb_impl.cc#L132 If oidx != 0 then using the current delete_head_nowait() call is correct. This is probably the major contribution to the CPU spinning. Maybe some other changes to the hdlc_framer block might help for high sample rates: 2. The block does a number of dynamic std:vector<> and pmt instantiations and destructions in a call to work(). If you use the oprofile tools, those likely generate some measureable overhead attributable to malloc() and atomic increments and decrements related to boost shared pointer for the PMTs. You might gain a few % CPU back by avoiding the constant allocation & deallocation by converting the block to use class variables where it makes sense. 3. The block also has 2 memcpy()'s in a call to work(). If you can figure out an way to optimize one away, you'll get some savings. I don't see an obvious way to do that right now. Also, your flowgraph does not have a throttle block to enforce a realistic timing for the sample rate you have chosen, so the hdlc_framer is going to run as fast as it can. The null sink essentially ensures there is always output buffer space for the hdlc_framer. > Thank you > Thanasis Regards, Andy _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
