btrace-perfetto

btrace Perfetto Trace Capture

Capture Perfetto traces with btrace 3.0 on a connected Android device, optionally comparing two branches. Opens results in Perfetto UI with a prefilled SQL query. After capture, query traces locally with trace_processor to compute comparison stats.

Prerequisites

Before starting, verify:

1. Connected device: adb devices shows a device (Android 8.0+, 64-bit)
2. btrace CLI jar: Check if tools/btrace/rhea-trace-shell.jar exists. If not, download it:

   mkdir -p tools/btrace/traces
   curl -sL "https://repo1.maven.org/maven2/com/bytedance/btrace/rhea-trace-processor/3.0.0/rhea-trace-processor-3.0.0.jar" \
     -o tools/btrace/rhea-trace-shell.jar
   

3. Perfetto trace_processor: Check if /tmp/trace_processor exists. If not, download it:

   # Download trace_processor (--fail ensures HTTP errors don't leave a file behind)
   curl -sSL --fail "https://get.perfetto.dev/trace_processor" -o /tmp/trace_processor
   
   # Verify magic bytes directly — file(1) output is too inconsistent across
   # versions/platforms to rely on for scripts or PIE binaries.
   magic=$(head -c 4 /tmp/trace_processor 2>/dev/null | od -An -vtx1 -N4 | tr -d ' \n')
   case "$magic" in
     2321*)                               ;; # #! shebang (script)
     7f454c46)                            ;; # ELF (Linux)
     cffaedfe|cefaedfe|feedfacf|feedface) ;; # Mach-O (macOS)
     cafebabe)                            ;; # Mach-O universal
     *)
       echo "Error: Downloaded file is not a valid script or executable (magic: ${magic:-empty})"
       rm -f /tmp/trace_processor
       exit 1
       ;;
   esac
   
   # Make executable only after verification
   chmod +x /tmp/trace_processor
   

4. Device ABI: Run adb shell getprop ro.product.cpu.abi — btrace only supports arm64-v8a and armeabi-v7a (no x86/x86_64)

Step 1: Parse Arguments