[Tools] Update linux_perf_report to split out GC.

tools/ignition/linux_perf_report.py

Index: tools/ignition/linux_perf_report.py
diff --git a/tools/ignition/linux_perf_report.py b/tools/ignition/linux_perf_report.py
index 69db37cbae4b276005a06e510e007378a0a96f8e..4e0b8844eae511abdc508bf0d5112a6885f2339c 100755
--- a/tools/ignition/linux_perf_report.py
+++ b/tools/ignition/linux_perf_report.py
@@ -54,6 +54,8 @@ COMPILER_SYMBOLS_RE = re.compile(
   r"v8::internal::(?:\(anonymous namespace\)::)?Compile|v8::internal::Parser")
 JIT_CODE_SYMBOLS_RE = re.compile(
   r"(LazyCompile|Compile|Eval|Script):(\*|~)")
+GC_SYMBOLS_RE = re.compile(
+  r"v8::internal::Heap::CollectGarbage")
 
 
 def strip_function_parameters(symbol):
@@ -74,7 +76,7 @@ def strip_function_parameters(symbol):
 
 def collapsed_callchains_generator(perf_stream, hide_other=False,
                                    hide_compiler=False, hide_jit=False,
-                                   show_full_signatures=False):
+                                   hide_gc=False, show_full_signatures=False):
   current_chain = []
   skip_until_end_of_chain = False
   compiler_symbol_in_chain = False
@@ -122,6 +124,11 @@ def collapsed_callchains_generator(perf_stream, hide_other=False,
         current_chain.append("[jit]")
         yield current_chain
         skip_until_end_of_chain = True
+    elif GC_SYMBOLS_RE.match(symbol):
+      if not hide_gc:
+        current_chain.append("[gc]")
+        yield current_chain
+        skip_until_end_of_chain = True
     elif symbol == "Stub:CEntryStub" and compiler_symbol_in_chain:
       if not hide_compiler:
         current_chain.append("[compiler]")
@@ -212,6 +219,11 @@ def parse_command_line():
     action="store_true"
   )
   command_line_parser.add_argument(
+    "--hide-gc",
+    help="Hide samples from garbage collection",
+    action="store_true"
+  )
+  command_line_parser.add_argument(
     "--show-full-signatures", "-s",
     help="show full signatures instead of function names",
     action="store_true"
@@ -237,7 +249,8 @@ def main():
 
   callchains = collapsed_callchains_generator(
     perf.stdout, program_options.hide_other, program_options.hide_compiler,
-    program_options.hide_jit, program_options.show_full_signatures)
+    program_options.hide_jit, program_options.hide_gc,
+    program_options.show_full_signatures)
 
   if program_options.output_flamegraph:
     write_flamegraph_input_file(program_options.output_stream, callchains)