Bug 670008. Fix measurement of the startup telemetry numbers. r=glandium

toolkit/components/startup/nsAppStartup.cpp

@@ -96,7 +96,11 @@
 #include <sys/sysctl.h>
 #endif
 
+#include "mozilla/Telemetry.h"
+
 static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
+
+using namespace mozilla;
 extern PRTime gXRE_mainTimestamp;
 extern PRTime gFirstPaintTimestamp;
 // mfinklesessionstore-browser-state-restored might be a better choice than the one below
@@ -574,11 +578,11 @@ JiffiesSinceBoot(const char *file)
   char *s = strrchr(stat, ')');
   if (!s)
     return 0;
-  sscanf(s + 2,
-         "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u "
-         "%*u %*u %*u %*u %*u %*d %*d %*d %*d %llu",
-         &starttime);
-  if (!starttime)
+  int ret = sscanf(s + 2,
+                   "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u "
+                   "%*u %*u %*u %*u %*u %*d %*d %*d %*d %llu",
+                   &starttime);
+  if (ret != 1 || !starttime)
     return 0;
   return starttime;
 }
@@ -595,7 +599,13 @@ ThreadedCalculateProcessCreationTimestamp(void *aClosure)
   char thread_stat[40];
   sprintf(thread_stat, "/proc/self/task/%d/stat", (pid_t) syscall(__NR_gettid));
   
-  PRTime interval = (JiffiesSinceBoot(thread_stat) - JiffiesSinceBoot("/proc/self/stat")) * PR_USEC_PER_SEC / hz;;
+  PRUint64 thread_jiffies = JiffiesSinceBoot(thread_stat);
+  PRUint64 self_jiffies = JiffiesSinceBoot("/proc/self/stat");
+  
+  if (!thread_jiffies || !self_jiffies)
+    return;
+
+  PRTime interval = (thread_jiffies - self_jiffies) * PR_USEC_PER_SEC / hz;
   gProcessCreationTimestamp = now - interval;
 }
 
@@ -628,7 +638,7 @@ CalculateProcessCreationTimestamp()
   timestamp = (timestamp - 116444736000000000LL) / 10LL;
 #else
   timestamp = (timestamp - 116444736000000000i64) / 10i64;
-#endif    
+#endif
   return timestamp;
 }
 #elif defined(XP_MACOSX)
@@ -686,6 +696,13 @@ MaybeDefineProperty(JSContext *cx, JSObject *obj, const char *name, PRTime times
   JS_DefineProperty(cx, obj, name, OBJECT_TO_JSVAL(date), NULL, NULL, JSPROP_ENUMERATE);     
 }
 
+enum {
+  INVALID_PROCESS_CREATION = 0,
+  INVALID_MAIN,
+  INVALID_FIRST_PAINT,
+  INVALID_SESSION_RESTORED
+};
+
 NS_IMETHODIMP
 nsAppStartup::GetStartupInfo()
 {
@@ -720,10 +737,28 @@ nsAppStartup::GetStartupInfo()
   } else if (!gProcessCreationTimestamp) {
     gProcessCreationTimestamp = CalculateProcessCreationTimestamp();
   }
+  // Bug 670008: Avoid obviously invalid process creation times
+  if (PR_Now() <= gProcessCreationTimestamp) {
+    gProcessCreationTimestamp = 0;
+    Telemetry::Accumulate(Telemetry::STARTUP_MEASUREMENT_ERRORS, INVALID_PROCESS_CREATION);
+  }
 
   MaybeDefineProperty(cx, obj, "process", gProcessCreationTimestamp);
-  MaybeDefineProperty(cx, obj, "main", gXRE_mainTimestamp);
-  MaybeDefineProperty(cx, obj, "firstPaint", gFirstPaintTimestamp);
-  MaybeDefineProperty(cx, obj, "sessionRestored", gRestoredTimestamp);
+
+  if (gXRE_mainTimestamp >= gProcessCreationTimestamp)
+    MaybeDefineProperty(cx, obj, "main", gXRE_mainTimestamp);
+  else
+    Telemetry::Accumulate(Telemetry::STARTUP_MEASUREMENT_ERRORS, INVALID_MAIN);
+
+  if (gFirstPaintTimestamp >= gXRE_mainTimestamp)
+    MaybeDefineProperty(cx, obj, "firstPaint", gFirstPaintTimestamp);
+  else
+    Telemetry::Accumulate(Telemetry::STARTUP_MEASUREMENT_ERRORS, INVALID_FIRST_PAINT);
+
+  if (gRestoredTimestamp >= gXRE_mainTimestamp)
+    MaybeDefineProperty(cx, obj, "sessionRestored", gRestoredTimestamp);
+  else
+    Telemetry::Accumulate(Telemetry::STARTUP_MEASUREMENT_ERRORS, INVALID_SESSION_RESTORED);
+
   return NS_OK;
 }

toolkit/components/telemetry/TelemetryHistograms.h

@@ -102,3 +102,4 @@ HTTP_HISTOGRAMS(SUB, "subitem: ")
 #undef HTTP_HISTOGRAMS
 HISTOGRAM(FIND_PLUGINS, 1, 3000, 10, EXPONENTIAL, "Time spent scanning filesystem for plugins (ms)")
 HISTOGRAM(CHECK_JAVA_ENABLED, 1, 3000, 10, EXPONENTIAL, "Time spent checking if Java is enabled (ms)")
+HISTOGRAM(STARTUP_MEASUREMENT_ERRORS, 1, 3, 4, LINEAR, "Flags errors in startup calculation()")

toolkit/components/telemetry/TelemetryPing.js

@@ -186,10 +186,12 @@ function getSimpleMeasurements() {
     // uptime in minutes
     uptime: Math.round((new Date() - si.process) / 60000)
   }
-  for each (let field in ["main", "firstPaint", "sessionRestored"]) {
-    if (!(field in si))
-      continue;
-    ret[field] = si[field] - si.process
+  if (si.process) {
+    for each (let field in ["main", "firstPaint", "sessionRestored"]) {
+      if (!(field in si))
+        continue;
+      ret[field] = si[field] - si.process
+    }
   }
   return ret;
 }