Benchmark tests for json-c

General strategy:

• Identify "after" commit hash
  • Use provided directory
  • Use provided commit hash
  • Local changes in current working directory
  • ${cur_branch}
• Identify "before" commit hash, in order of preference
  • Use provided directory
  • Use provided commit hash
  • Use origin/${cur_branch}, if different from ${after_commit}
  • Use previous release

• If not using existing dir, clone to src-${after_commit}

  • or, checkout appropriate commit in existing src-${after_commit}
• Create build & install dirs for ${after_commit}
• Build & install ${after_commit}
• Compile benchmark programs against install-${after_commit}

• If not using existing dir, clone to src-${before_commit}

  • or, checkout appropriate commit in existing src-${before_commit}
• Create build & install dirs for ${before_commit}
• Build & install ${before_commit}
• Compile benchmark programs against install-${before_commit}

• Run benchmark in each location

• Compare results

heaptrack memory profiler

https://milianw.de/blog/heaptrack-a-heap-memory-profiler-for-linux.html

yum install libdwarf-devel elfutils boost-devel libunwind-devel

git clone git://anongit.kde.org/heaptrack
cd heaptrack
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo \
	-DCMAKE_INSTALL_PREFIX=$HOME/heaptrack-install ..
make install

Issues

• jc-bench.sh is incomplete.

• valgrind massif misreports "extra-heap" bytes?

  "json_parse -n canada.json" shows 38640 KB maxrss.

  Using valgrind --tool=massif, a large amount of memory is listed as
  wasted "extra-heap" bytes. (~5.6MB)

  valgrind --tool=massif --massif-out-file=massif.out ./json_parse -n ~/canada.json
  ms_print massif.out
  

Using heaptrack, and analyzing the histogram, only shows ~2.6MB
```
heaptrack ./json_parse -n canada.json
heaptrack --analyze heaptrack*gz -H histogram.out
awk ' { s=$1; count=$2; ru=(int((s+ 15) / 16)) * 16; wasted = ((ru-s)*count); print s, count, ru-s, wasted; total=total+wasted} END { print "Total: ", total }' histogram.out
```

With the (unreleased) arraylist trimming changes, maxrss reported by
getrusage() goes down, but massif claims more total usage, and a HUGE
extra-heap amount (50% of total).