Home

Quick how-to for generating profiles with this tool:

1. kenv kern.hwpmc.callchaindepth="32"

• put 'kern.hwpmc.callchaindepth="32"' in /boot/loader.conf to persist this across a reboot

1. kldload hwpmc
2. pmcstat -S unhalted-cycles -O samples.out sleep 10

• Collect samples for 10 seconds

2. limits -v 4G pmcprofiler -f samples.out -F flame.out

• Generate flamegraph input

3. flamegraph.pl < flame.out > flame.svg

• FlameGraph can be checked out here: https://github.com/brendangregg/FlameGraph

Other options to pmcprofiler:

• -o flat
• Generate flat (no callchain) output, including a per-instruction view
• -G leaf
• Generate text-based callchain output, starting from leaf functions and moving up the stack
• -r root
• Generate text-based callchain output, starting from the root of the callchain and moving down the stack
• -N kernel
• Specify alternate kernel file (default is $(sysctl kern.bootfile))
• -m module path
• Specify alternate module path (default is $(sysctl kern.module_path))