From b92ab8df04c4bcd81e50e44bafaad9e488a24f66 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishearth@gmail.com>
Date: Tue, 28 Nov 2017 03:16:26 -0800
Subject: [PATCH] Bug 1421195 - Add telemetry probe for fraction of restyles
 that are parallel ; r=emilio

MozReview-Commit-ID: sVN7CWjgni
---
 layout/style/ServoBindings.cpp               | 12 ++++++++++++
 layout/style/ServoBindings.h                 |  1 +
 toolkit/components/telemetry/Histograms.json | 10 ++++++++++
 3 files changed, 23 insertions(+)

diff --git a/layout/style/ServoBindings.cpp b/layout/style/ServoBindings.cpp
index 1b8c03cad2d6..ea37fd20134e 100644
--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -65,6 +65,7 @@
 #include "mozilla/StyleAnimationValue.h"
 #include "mozilla/SystemGroup.h"
 #include "mozilla/ServoMediaList.h"
+#include "mozilla/Telemetry.h"
 #include "mozilla/RWLock.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/ElementInlines.h"
@@ -122,6 +123,17 @@ AssertIsMainThreadOrServoLangFontPrefsCacheLocked()
   MOZ_ASSERT(NS_IsMainThread() || sServoFFILock->LockedForWritingByCurrentThread());
 }
 
+
+void
+Gecko_RecordTraversalStatistics(uint32_t total, uint32_t parallel)
+{
+  // we ignore cases where a page just didn't restyle a lot
+  if (total > 30) {
+    uint32_t percent = parallel * 100 / total;
+    Telemetry::Accumulate(Telemetry::STYLO_PARALLEL_RESTYLE_FRACTION, percent);
+  }
+}
+
 bool
 Gecko_IsInDocument(RawGeckoNodeBorrowed aNode)
 {
diff --git a/layout/style/ServoBindings.h b/layout/style/ServoBindings.h
index 7046e02d1423..18774b73f592 100644
--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -142,6 +142,7 @@ struct FontSizePrefs
 };
 
 // DOM Traversal.
+void Gecko_RecordTraversalStatistics(uint32_t total, uint32_t parallel);
 bool Gecko_IsInDocument(RawGeckoNodeBorrowed node);
 bool Gecko_FlattenedTreeParentIsParent(RawGeckoNodeBorrowed node);
 bool Gecko_IsSignificantChild(RawGeckoNodeBorrowed node,
diff --git a/toolkit/components/telemetry/Histograms.json b/toolkit/components/telemetry/Histograms.json
index bd332c02beb6..1811f17ad065 100644
--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -13931,5 +13931,15 @@
     "expires_in_version": "60",
     "kind": "boolean",
     "description": "Tracking how often scripts are loaded with a 'valid' version parameter. This telemetry ID helps us to decide if and when remove the support of script versioning."
+  },
+  "STYLO_PARALLEL_RESTYLE_FRACTION": {
+    "record_in_processes": ["content"],
+    "alert_emails": ["manish@mozilla.com"],
+    "expires_in_version": "60",
+    "kind": "linear",
+    "high": 100,
+    "n_buckets": 50,
+    "description": "Fraction of restyles on a single page that were parallel",
+    "bug_numbers": [1421195]
   }
 }