Bug 1734597 - Make about:processes fallback to cycle count to decide if a thread or process is active to workaround low CPU timing precision on Windows, r=dthayer,fluent-reviewers,flod.

Differential Revision: https://phabricator.services.mozilla.com/D127813

dom/chrome-webidl/ChromeUtils.webidl

@@ -631,6 +631,7 @@ enum WebIDLProcType {
 dictionary ThreadInfoDictionary {
   long long tid = 0;
   DOMString name = "";
+  unsigned long long cpuCycleCount = 0;
   unsigned long long cpuUser = 0;
   unsigned long long cpuKernel = 0;
 };
@@ -684,6 +685,11 @@ dictionary ChildProcInfoDictionary {
   // Time spent by the process in kernel mode, in ns.
   unsigned long long cpuKernel = 0;
 
+  // Total CPU cycles used by this process.
+  // On Windows where the resolution of CPU timings is 16ms, this can
+  // be used to determine if a process is idle or slightly active.
+  unsigned long long cpuCycleCount = 0;
+
   // Thread information for this process.
   sequence<ThreadInfoDictionary> threads = [];
 
@@ -727,6 +733,11 @@ dictionary ParentProcInfoDictionary {
   // Time spent by the process in kernel mode, in ns.
   unsigned long long cpuKernel = 0;
 
+  // Total CPU cycles used by this process.
+  // On Windows where the resolution of CPU timings is 16ms, this can
+  // be used to determine if a process is idle or slightly active.
+  unsigned long long cpuCycleCount = 0;
+
   // Thread information for this process.
   sequence<ThreadInfoDictionary> threads = [];
 

toolkit/components/aboutprocesses/content/aboutProcesses.js

@@ -34,6 +34,9 @@ const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 const { XPCOMUtils } = ChromeUtils.import(
   "resource://gre/modules/XPCOMUtils.jsm"
 );
+const { AppConstants } = ChromeUtils.import(
+  "resource://gre/modules/AppConstants.jsm"
+);
 
 XPCOMUtils.defineLazyModuleGetters(this, {
   ContextualIdentityService:
@@ -219,15 +222,10 @@ var State = {
     let result = {
       tid: cur.tid,
       name: cur.name || `(${cur.tid})`,
-      // Total amount of CPU used, in ns (user).
-      totalCpuUser: cur.cpuUser,
-      slopeCpuUser: null,
-      // Total amount of CPU used, in ns (kernel).
-      totalCpuKernel: cur.cpuKernel,
-      slopeCpuKernel: null,
       // Total amount of CPU used, in ns (user + kernel).
       totalCpu: cur.cpuUser + cur.cpuKernel,
       slopeCpu: null,
+      active: null,
     };
     if (!prev) {
       return result;
@@ -235,9 +233,9 @@ var State = {
     if (prev.tid != cur.tid) {
       throw new Error("Assertion failed: A thread cannot change tid.");
     }
-    result.slopeCpuUser = (cur.cpuUser - prev.cpuUser) / deltaT;
-    result.slopeCpuKernel = (cur.cpuKernel - prev.cpuKernel) / deltaT;
-    result.slopeCpu = result.slopeCpuKernel + result.slopeCpuUser;
+    result.slopeCpu =
+      (cur.cpuUser + cur.cpuKernel - prev.cpuUser - prev.cpuKernel) / deltaT;
+    result.active = !!result.slopeCpu || cur.cpuCycleCount > prev.cpuCycleCount;
     return result;
   },
 
@@ -314,12 +312,9 @@ var State = {
       filename: cur.filename,
       totalRamSize: cur.memory,
       deltaRamSize: null,
-      totalCpuUser: cur.cpuUser,
-      slopeCpuUser: null,
-      totalCpuKernel: cur.cpuKernel,
-      slopeCpuKernel: null,
       totalCpu: cur.cpuUser + cur.cpuKernel,
       slopeCpu: null,
+      active: null,
       type: cur.type,
       origin: cur.origin || "",
       threads: null,
@@ -366,9 +361,9 @@ var State = {
       });
     }
     result.deltaRamSize = cur.memory - prev.memory;
-    result.slopeCpuUser = (cur.cpuUser - prev.cpuUser) / deltaT;
-    result.slopeCpuKernel = (cur.cpuKernel - prev.cpuKernel) / deltaT;
-    result.slopeCpu = result.slopeCpuUser + result.slopeCpuKernel;
+    result.slopeCpu =
+      (cur.cpuUser + cur.cpuKernel - prev.cpuUser - prev.cpuKernel) / deltaT;
+    result.active = !!result.slopeCpu || cur.cpuCycleCount > prev.cpuCycleCount;
     result.threads = threads;
     return result;
   },
@@ -471,6 +466,46 @@ var View = {
     return row;
   },
 
+  displayCpu(data, cpuCell) {
+    if (data.slopeCpu == null) {
+      this._fillCell(cpuCell, {
+        fluentName: "about-processes-cpu-user-and-kernel-not-ready",
+        classes: ["cpu"],
+      });
+    } else {
+      let { duration, unit } = this._getDuration(data.totalCpu);
+      if (data.totalCpu == 0 && AppConstants.platform == "win") {
+        // The minimum non zero CPU time we can get on Windows is 16ms
+        // so avoid displaying '0ns'.
+        unit = "ms";
+      }
+      let localizedUnit = gLocalizedUnits.duration[unit];
+      if (data.slopeCpu == 0) {
+        let fluentName = data.active
+          ? "about-processes-cpu-almost-idle"
+          : "about-processes-cpu-fully-idle";
+        this._fillCell(cpuCell, {
+          fluentName,
+          fluentArgs: {
+            total: duration,
+            unit: localizedUnit,
+          },
+          classes: ["cpu"],
+        });
+      } else {
+        this._fillCell(cpuCell, {
+          fluentName: "about-processes-cpu",
+          fluentArgs: {
+            percent: data.slopeCpu,
+            total: duration,
+            unit: localizedUnit,
+          },
+          classes: ["cpu"],
+        });
+      }
+    }
+  },
+
   /**
    * Display a row showing a single process (without its threads).
    *
@@ -682,37 +717,9 @@ var View = {
       }
     }
 
-    // Column: CPU: User and Kernel
+    // Column: CPU
     let cpuCell = memoryCell.nextSibling;
-    if (data.slopeCpu == null) {
-      this._fillCell(cpuCell, {
-        fluentName: "about-processes-cpu-user-and-kernel-not-ready",
-        classes: ["cpu"],
-      });
-    } else {
-      let { duration, unit } = this._getDuration(data.totalCpu);
-      let localizedUnit = gLocalizedUnits.duration[unit];
-      if (data.slopeCpu == 0) {
-        this._fillCell(cpuCell, {
-          fluentName: "about-processes-cpu-idle",
-          fluentArgs: {
-            total: duration,
-            unit: localizedUnit,
-          },
-          classes: ["cpu"],
-        });
-      } else {
-        this._fillCell(cpuCell, {
-          fluentName: "about-processes-cpu",
-          fluentArgs: {
-            percent: data.slopeCpu,
-            total: duration,
-            unit: localizedUnit,
-          },
-          classes: ["cpu"],
-        });
-      }
-    }
+    this.displayCpu(data, cpuCell);
 
     // Column: Kill button – but not for all processes.
     let killButton = cpuCell.nextSibling;
@@ -764,7 +771,7 @@ var View = {
     let activeThreads = new Map();
     let activeThreadCount = 0;
     for (let t of data.threads) {
-      if (!t.slopeCpu) {
+      if (!t.active) {
         continue;
       }
       ++activeThreadCount;
@@ -928,37 +935,8 @@ var View = {
       classes: ["name", "double_indent"],
     });
 
-    // Column: CPU: User and Kernel
-    let cpuCell = nameCell.nextSibling;
-    if (data.slopeCpu == null) {
-      this._fillCell(cpuCell, {
-        fluentName: "about-processes-cpu-user-and-kernel-not-ready",
-        classes: ["cpu"],
-      });
-    } else {
-      let { duration, unit } = this._getDuration(data.totalCpu);
-      let localizedUnit = gLocalizedUnits.duration[unit];
-      if (data.slopeCpu == 0) {
-        this._fillCell(cpuCell, {
-          fluentName: "about-processes-cpu-idle",
-          fluentArgs: {
-            total: duration,
-            unit: localizedUnit,
-          },
-          classes: ["cpu"],
-        });
-      } else {
-        this._fillCell(cpuCell, {
-          fluentName: "about-processes-cpu",
-          fluentArgs: {
-            percent: data.slopeCpu,
-            total: duration,
-            unit: localizedUnit,
-          },
-          classes: ["cpu"],
-        });
-      }
-    }
+    // Column: CPU
+    this.displayCpu(data, nameCell.nextSibling);
 
     // Third column (Buttons) is empty, nothing to do.
   },
@@ -1338,6 +1316,11 @@ var Control = {
     // Used by tests to differentiate full updates from l10n updates.
     document.dispatchEvent(new CustomEvent("AboutProcessesUpdated"));
   },
+  _compareCpu(a, b) {
+    return (
+      b.slopeCpu - a.slopeCpu || b.active - a.active || b.totalCpu - a.totalCpu
+    );
+  },
   _showThreads(row) {
     let process = row.process;
     this._sortThreads(process.threads);
@@ -1353,7 +1336,7 @@ var Control = {
           order = a.name.localeCompare(b.name) || a.tid - b.tid;
           break;
         case "column-cpu-total":
-          order = b.slopeCpu - a.slopeCpu;
+          order = this._compareCpu(a, b);
           break;
         case "column-memory-resident":
         case null:
@@ -1379,7 +1362,7 @@ var Control = {
             a.pid - b.pid;
           break;
         case "column-cpu-total":
-          order = b.slopeCpu - a.slopeCpu;
+          order = this._compareCpu(a, b);
           break;
         case "column-memory-resident":
           order = b.totalRamSize - a.totalRamSize;

toolkit/components/aboutprocesses/tests/browser/head.js

@@ -634,7 +634,7 @@ async function testAboutProcessesWithConfig({ showAllFrames, showThreads }) {
         number,
         "The number of active threads should not exceed the total number of threads"
       );
-      let activeThreads = row.process.threads.filter(t => t.slopeCpu);
+      let activeThreads = row.process.threads.filter(t => t.active);
       Assert.equal(
         active,
         activeThreads.length,

toolkit/components/processtools/ProcInfo.h

@@ -60,6 +60,7 @@ struct ThreadInfo {
   uint64_t cpuUser = 0;
   // System time in ns.
   uint64_t cpuKernel = 0;
+  uint64_t cpuCycleCount = 0;
 };
 
 // Info on a DOM window.
@@ -111,6 +112,7 @@ struct ProcInfo {
   uint64_t cpuUser = 0;
   // System time in ns.
   uint64_t cpuKernel = 0;
+  uint64_t cpuCycleCount = 0;
   // Threads owned by this process.
   CopyableTArray<ThreadInfo> threads;
   // DOM windows represented by this process.
@@ -213,6 +215,7 @@ nsresult CopySysProcInfoToDOM(const ProcInfo& source, T* dest) {
   dest->mMemory = source.memory;
   dest->mCpuUser = source.cpuUser;
   dest->mCpuKernel = source.cpuKernel;
+  dest->mCpuCycleCount = source.cpuCycleCount;
 
   // Copy thread info.
   mozilla::dom::Sequence<mozilla::dom::ThreadInfoDictionary> threads;
@@ -224,6 +227,7 @@ nsresult CopySysProcInfoToDOM(const ProcInfo& source, T* dest) {
     }
     thread->mCpuUser = entry.cpuUser;
     thread->mCpuKernel = entry.cpuKernel;
+    thread->mCpuCycleCount = entry.cpuCycleCount;
     thread->mTid = entry.tid;
     thread->mName.Assign(entry.name);
   }

toolkit/components/processtools/ProcInfo_win.cpp

@@ -91,6 +91,8 @@ RefPtr<ProcInfoPromise> GetProcInfo(nsTArray<ProcInfoRequest>&& aRequests) {
           info.filename.Assign(filename);
           info.cpuKernel = ToNanoSeconds(kernelTime);
           info.cpuUser = ToNanoSeconds(userTime);
+          QueryProcessCycleTime(handle.get(), &info.cpuCycleCount);
+
           info.memory = memoryCounters.PrivateUsage;
 
           if (!gathered.put(request.pid, std::move(info))) {
@@ -157,6 +159,8 @@ RefPtr<ProcInfoPromise> GetProcInfo(nsTArray<ProcInfoRequest>&& aRequests) {
             threadInfo->cpuUser = ToNanoSeconds(userTime);
           }
 
+          QueryThreadCycleTime(hThread.get(), &threadInfo->cpuCycleCount);
+
           // Attempt to get thread name.
           // If we fail, continue without this piece of information.
           if (getThreadDescription) {

toolkit/locales/en-US/toolkit/about/aboutProcesses.ftl

@@ -138,9 +138,14 @@ about-processes-cpu = { NUMBER($percent, maximumSignificantDigits: 2, style: "pe
 # Special case: data is not available yet.
 about-processes-cpu-user-and-kernel-not-ready = (measuring)
 
+# Special case: process or thread is almost idle (using less than 0.1% of a CPU core).
+# This case only occurs on Windows where the precision of the CPU times is low.
+about-processes-cpu-almost-idle = < 0.1%
+    .title = Total CPU time: { NUMBER($total, maximumFractionDigits: 0) }{ $unit }
+
 # Special case: process or thread is currently idle.
-about-processes-cpu-idle = idle
-    .title = Total CPU time: { NUMBER($total, maximumFractionDigits: 2) }{ $unit }
+about-processes-cpu-fully-idle = idle
+    .title = Total CPU time: { NUMBER($total, maximumFractionDigits: 0) }{ $unit }
 
 ## Displaying Memory (total and delta)
 ## Variables: