New flag --perf_basic_prof_only_functions

Restricts linux perf-event code range reporting to functions only (i.e. on
stubs.) While this makes the gathered ticks less accurate, it reduces the
growth of the /tmp/perf-${pid}.map file.

BUG=v8:3453
R=hablich@chromium.org,danno@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1292743002

Cr-Commit-Position: refs/heads/master@{#30179}

src/flag-definitions.h

@@ -943,6 +943,9 @@ DEFINE_BOOL(ll_prof, false, "Enable low-level linux profiler.")
 DEFINE_BOOL(perf_basic_prof, false,
             "Enable perf linux profiler (basic support).")
 DEFINE_NEG_IMPLICATION(perf_basic_prof, compact_code_space)
+DEFINE_BOOL(perf_basic_prof_only_functions, false,
+            "Only report function code ranges to perf (i.e. no stubs).")
+DEFINE_IMPLICATION(perf_basic_prof_only_functions, perf_basic_prof)
 DEFINE_STRING(gc_fake_mmap, "/tmp/__v8_gc__",
               "Specify the name of the file for fake gc mmap used in ll_prof")
 DEFINE_BOOL(log_internal_timer_events, false, "Time internal events.")

src/log.cc

@@ -288,6 +288,12 @@ void PerfBasicLogger::LogRecordedBuffer(Code* code,
                                        int length) {
   DCHECK(code->instruction_start() == code->address() + Code::kHeaderSize);
 
+  if (FLAG_perf_basic_prof_only_functions &&
+      (code->kind() != Code::FUNCTION &&
+       code->kind() != Code::OPTIMIZED_FUNCTION)) {
+    return;
+  }
+
   base::OS::FPrint(perf_output_handle_, "%llx %x %.*s\n",
                    reinterpret_cast<uint64_t>(code->instruction_start()),
                    code->instruction_size(), length, name);