Bug 1650151 - Merge webIsolated processes when diffing with non-Fissi…

…on memory reports. r=njn

Fission processes show up in about:memory as webIsolated=<URL>. This is
great when comparing two reports from a single session, to precisely
see how the memory usage of a particular process has changed, but it
makes it harder to compare to a non-Fission memory report. For instance,
when loading a news page with many ad iframes, what was a single process
without Fission enabled will be split across more than a dozen processes.

This patch fixes this by making it so that if exactly one memory report
being diffed contains a webIsolated process, then webIsolated processes
will be treated like regular web processes.

Differential Revision: https://phabricator.services.mozilla.com/D85608

toolkit/components/aboutmemory/content/aboutMemory.js

@@ -935,15 +935,31 @@ DReport.PRESENT_IN_FIRST_ONLY = 1;
 DReport.PRESENT_IN_SECOND_ONLY = 2;
 DReport.ADDED_FOR_BALANCE = 3;
 
+/**
+ * Return true if the report contains a webIsolated process,
+ * which is a good indication that Fission is enabled.
+ */
+function hasWebIsolatedProcess(aJSONReports) {
+  for (let jr of aJSONReports) {
+    assert(jr.process !== undefined, "Missing process");
+    if (jr.process.startsWith("webIsolated")) {
+      return true;
+    }
+  }
+  return false;
+}
+
 /**
  * Make a report map, which has combined path+process strings for keys, and
  * DReport objects for values.
  *
  * @param aJSONReports
  *        The |reports| field of a JSON object.
+ * @param aForgetIsolation
+          If this is true, treat webIsolated processes like web processes.
  * @return The constructed report map.
  */
-function makeDReportMap(aJSONReports) {
+function makeDReportMap(aJSONReports, aForgetIsolation) {
   let dreportMap = {};
   for (let jr of aJSONReports) {
     assert(jr.process !== undefined, "Missing process");
@@ -968,6 +984,10 @@ function makeDReportMap(aJSONReports) {
     let process = jr.process.replace(pidRegex, pidSubst);
     let path = jr.path.replace(pidRegex, pidSubst);
 
+    if (aForgetIsolation && process.startsWith("webIsolated")) {
+      process = "web (pid NNN)";
+    }
+
     // Strip TIDs and threadpool IDs.
     path = path.replace(/\(tid=(\d+)\)/, "(tid=NNN)");
     path = path.replace(/#\d+ \(tid=NNN\)/, "#N (tid=NNN)");
@@ -1103,15 +1123,25 @@ function diffJSONObjects(aJson1, aJson2) {
     return aJson1[aProp];
   }
 
+  // If one report we're diffing contains webIsolated processes, but the other
+  // does not, then we're probably comparing a report with Fission enabled with
+  // one where it is not enabled. In this case, we want to make all of the
+  // webIsolated processes look like plain old web processes to get a better
+  // diff.
+  let hasIsolated1 = hasWebIsolatedProcess(aJson1.reports);
+  let hasIsolated2 = hasWebIsolatedProcess(aJson2.reports);
+  let eitherIsolated = hasIsolated1 || hasIsolated2;
+  let forgetIsolation = hasIsolated1 != hasIsolated2 && eitherIsolated;
+
   return {
     version: simpleProp("version"),
 
     hasMozMallocUsableSize: simpleProp("hasMozMallocUsableSize"),
 
     reports: makeJSONReports(
       diffDReportMaps(
-        makeDReportMap(aJson1.reports),
-        makeDReportMap(aJson2.reports)
+        makeDReportMap(aJson1.reports, forgetIsolation),
+        makeDReportMap(aJson2.reports, forgetIsolation)
       )
     ),
   };

toolkit/components/aboutmemory/tests/chrome.ini

@@ -4,6 +4,8 @@ support-files =
   crash-dump-diff1.json
   crash-dump-diff2.json
   crash-dump-good.json
+  fiss-diff1.json
+  fiss-diff2.json
   memory-reports-bad.json
   memory-reports-diff1.json
   memory-reports-diff2.json

toolkit/components/aboutmemory/tests/fiss-diff1.json

@@ -0,0 +1,18 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {"process": "P (pid 12345)", "path": "explicit/foobar", "kind": 1, "units": 0, "amount": 100, "description": "Desc."},
+      {"process": "P (pid 12345)", "path": "explicit/zero1", "kind": 1, "units": 0, "amount": 0, "description": "Desc."},
+      {"process": "P (pid 12345)", "path": "heap-allocated", "kind": 2, "units": 0, "amount": 10000000, "description": "Heap allocated."},
+
+      {"process": "web (pid 12345)", "path": "explicit/a/b", "kind": 1, "units": 0, "amount": 2000000, "description": "Desc."},
+      {"process": "web (pid 12345)", "path": "explicit/a/c/d", "kind": 1, "units": 0, "amount": 2000000, "description": "Desc."},
+      {"process": "web (pid 12345)", "path": "heap-allocated", "kind": 2, "units": 0, "amount": 10000000, "description": "Heap allocated."}
+    ]
+  }
+}
+

toolkit/components/aboutmemory/tests/fiss-diff2.json

@@ -0,0 +1,18 @@
+{
+  "foo": 1,
+  "blah": 2,
+  "memory_report": {
+    "version": 1,
+    "hasMozMallocUsableSize": true,
+    "reports": [
+      {"process": "P (pid 12345)", "path": "explicit/foobar", "kind": 1, "units": 0, "amount": 400, "description": "Desc."},
+      {"process": "P (pid 12345)", "path": "explicit/zero1", "kind": 1, "units": 0, "amount": 0, "description": "Desc."},
+      {"process": "P (pid 12345)", "path": "heap-allocated", "kind": 2, "units": 0, "amount": 13000000, "description": "Heap allocated."},
+
+      {"process": "webIsolated=https://example.com (pid 12345)", "path": "explicit/a/b", "kind": 1, "units": 0, "amount": 2000000, "description": "Desc."},
+      {"process": "webIsolated=https://example.com (pid 12345)", "path": "explicit/a/c/d", "kind": 1, "units": 0, "amount": 3000000, "description": "Desc."},
+      {"process": "webIsolated=https://example.com (pid 12345)", "path": "heap-allocated", "kind": 2, "units": 0, "amount": 12000000, "description": "Heap allocated."}
+    ]
+  }
+}
+

toolkit/components/aboutmemory/tests/test_aboutmemory3.xhtml

@@ -495,6 +495,34 @@ Other Measurements\n\
 1 B ── heap-allocated\n\
 \n\
 End of Main Process (pid NNN)\n\
+";
+
+  let expectedDiffFiss =
+"\
+P (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+3,000,000 B (100.0%) -- explicit\n\
+├──2,999,700 B (99.99%) ── heap-unclassified\n\
+└────────300 B (00.01%) ── foobar\n\
+\n\
+Other Measurements\n\
+\n\
+3,000,000 B ── heap-allocated\n\
+\n\
+End of P (pid NNN)\n\
+web (pid NNN)\n\
+Explicit Allocations\n\
+\n\
+2,000,000 B (100.0%) -- explicit\n\
+├──1,000,000 B (50.00%) ── a/c/d\n\
+└──1,000,000 B (50.00%) ── heap-unclassified\n\
+\n\
+Other Measurements\n\
+\n\
+2,000,000 B ── heap-allocated\n\
+\n\
+End of web (pid NNN)\n\
 ";
 
   let frames = [
@@ -518,7 +546,10 @@ End of Main Process (pid NNN)\n\
     { filename: "memory-reports-diff1.json", filename2: "memory-reports-diff2.json", expected: expectedDiffVerbose, dumpFirst: false, verbose: true },
 
     // This diffs two pre-existing crash report files.
-    { filename: "crash-dump-diff1.json", filename2: "crash-dump-diff2.json", expected: expectedDiff2, dumpFirst: false, verbose: true }
+    { filename: "crash-dump-diff1.json", filename2: "crash-dump-diff2.json", expected: expectedDiff2, dumpFirst: false, verbose: true },
+
+    // This diffs a non-Fission and a Fission memory report.
+    { filename: "fiss-diff1.json", filename2: "fiss-diff2.json", expected: expectedDiffFiss, dumpFirst: false, verbose: true }
   ];
 
   SimpleTest.waitForFocus(chain(frames));