dwarf-assembly/benching

Benching eh_elfs

Benchmark setup

Pick some name for your eh_elfs directory. We will call it $EH_ELF_DIR.

Generate the eh_elfs

../../generate_eh_elf.py --deps -o "$EH_ELF_DIR" \
  --keep-holes -O2 --global-switch --enable-deref-arg "$BENCHED_BINARY"

Record a perf session

perf record --call-graph dwarf,4096 "$BENCHED_BINARY" [args]

Set up the environment

source ../../env/apply [vanilla | vanilla-nocache | *eh_elf] [dbg | *release]

The first value selects the version of libunwind you will be running, the second selects whether you want to run in debug or release mode (use release to get readings, debug to check for errors).

You can reset your environment to its previous state by running deactivate.

If you pick the eh_elf flavour, you will also have to

export LD_LIBRARY_PATH="$EH_ELF_DIR:$LD_LIBRARY_PATH"

Extract results

Base readings

In release mode (faster), run

perf report 2>&1 >/dev/null

with both eh_elf and vanilla shells. Compare average time.

Getting debug output

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null

Total number of calls to unw_step

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null | grep -c "step:.* returning"

Total number of vanilla errors

With the vanilla context,

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null | grep -c "step:.* returning -"

Total number of fallbacks to original DWARF

With the eh_elf context,

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null | grep -c "step:.* falling back"

Total number of fallbacks to original DWARF that actually used DWARF

With the eh_elf context,

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null | grep -c "step:.* fallback with"

Get succeeded fallback locations

UNW_DEBUG_LEVEL=5 perf report 2>&1 >/dev/null \
  | grep "step: .* fallback with" -B 15 \
  | grep "In memory map" | sort | uniq -c