UAVCAN performance audit (#6829)

* UAVCAN ESC output: removing ESC output channels from published message that are always zero. This allows the UAVCAN stack to always transfer only the minimum number of output values, avoiding redundant zeroes and the associated increase in bus load and CPU time

* Added a separate mixer file for CAN quadrotor

* Sampling profiler improvements

* PMSP: Output more endpoints

* Matrix update

* libc usage workaround

* Removed UAVCAN perfcounters

Debug/poor-mans-profiler.sh

@@ -1,12 +1,20 @@
 #!/bin/bash
 #
+# Author: Pavel Kirienko <pavel.kirienko@zubax.com>
+#
 # Poor man's sampling profiler for NuttX.
 #
 # Usage: Install flamegraph.pl in your PATH, configure your .gdbinit, run the script with proper arguments and go
 #        have a coffee. When you're back, you'll see the flamegraph. Note that frequent calls to GDB significantly
 #        interfere with normal operation of the target, which means that you can't profile real-time tasks with it.
+#        For best results, ensure that the PC is not overloaded, the USB host controller to which the debugger is
+#        connected is not congested. You should also allow the current user to set negative nice values.
 #
-# Requirements: ARM GDB with Python support
+# The FlameGraph script can be downloaded from https://github.com/brendangregg/FlameGraph. Thanks Mr. Gregg.
+#
+# Requirements: ARM GDB with Python support. You can get one by downloading the sources from
+#               https://launchpad.net/gcc-arm-embedded and building them with correct flags.
+#               Note that Python support is not required if no per-task sampling is needed.
 #
 
 set -e
@@ -33,7 +41,7 @@ which flamegraph.pl > /dev/null || die "Install flamegraph.pl first"
 nsamples=0
 sleeptime=0.1    # Doctors recommend 7-8 hours a day
 taskname=
-elf=$root/Build/px4fmu-v2_default.build/firmware.elf
+elf=
 append=0
 fgfontsize=10
 fgwidth=1900
@@ -69,6 +77,8 @@ do
     shift
 done
 
+[[ -z "$elf" ]] && die "Please specify the ELF file location, e.g.: build_px4fmu-v4_default/src/firmware/nuttx/firmware_nuttx"
+
 #
 # Temporary files
 #
@@ -237,8 +247,8 @@ for s, f in sorted(stacks.items(), key=lambda (s, f): s):
 
 print('Total stack frames:', num_stack_frames, file=sys.stderr)
 print('Top consumers (distribution of the stack tops):', file=sys.stderr)
-for name,num in sorted(stack_tops.items(), key=lambda (name, num): num, reverse=True)[:10]:
-    print('% 5.1f%%   ' % (100 * num / num_stack_frames), name, file=sys.stderr)
+for name,num in sorted(stack_tops.items(), key=lambda (name, num): num, reverse=True)[:300]:
+    print('% 7.3f%%   ' % (100 * num / num_stack_frames), name, file=sys.stderr)
 EOF
 
 cat $stacksfile | python /tmp/pmpn-folder.py > $foldfile