Bug 1630448 - MOZ_PROFILER_STARTUP_NO_BASE=1 prevents Base Profiler from running when MOZ_PROFILER_STARTUP is set - r=canaltinova

The Base Profiler is still recent and barely used, so it may contain some bugs.
With bug 1586939, the Base Profiler is now used more often because it is controlled the same way as the Gecko Profiler.
This has surfaced some intermittent issues, which pollute existing tests.

Until the root cause is found (see bug 1648325), setting `MOZ_PROFILER_STARTUP_NO_BASE=1` prevents the Base Profiler from running. This may be used where problems are visible, to diagnostic them and/or reduce them where needed.

Differential Revision: https://phabricator.services.mozilla.com/D81018

mozglue/baseprofiler/core/platform.cpp

@@ -2552,6 +2552,13 @@ void profiler_init(void* aStackTop) {
       return;
     }
 
+    // Hidden option to stop Base Profiler, mostly due to Talos intermittents,
+    // see https://bugzilla.mozilla.org/show_bug.cgi?id=1638851#c3
+    // TODO: Investigate root cause and remove this in bugs 1648324 and 1648325.
+    if (getenv("MOZ_PROFILER_STARTUP_NO_BASE")) {
+      return;
+    }
+
     LOG("- MOZ_PROFILER_STARTUP is set");
 
     // Startup default capacity may be different.

tools/profiler/core/platform.cpp

@@ -4052,6 +4052,14 @@ void GetProfilerEnvVarsForChildProcess(
   }
 
   aSetEnv("MOZ_PROFILER_STARTUP", "1");
+
+  // Hidden option to stop Base Profiler, mostly due to Talos intermittents,
+  // see https://bugzilla.mozilla.org/show_bug.cgi?id=1638851#c3
+  // TODO: Investigate root cause and remove this in bugs 1648324 and 1648325.
+  if (getenv("MOZ_PROFILER_STARTUP_NO_BASE")) {
+    aSetEnv("MOZ_PROFILER_STARTUP_NO_BASE", "1");
+  }
+
   auto capacityString =
       Smprintf("%u", unsigned(ActivePS::Capacity(lock).Value()));
   aSetEnv("MOZ_PROFILER_STARTUP_ENTRIES", capacityString.get());