[scudo] Add the record of number of attempted page release (#120497)

This also removes the `RangesReleased` which doesn't give much insight
to whether we should adjust the heuristic of doing page release.

compiler-rt/lib/scudo/standalone/primary32.h

@@ -387,7 +387,7 @@ private:
 
   struct ReleaseToOsInfo {
     uptr BytesInFreeListAtLastCheckpoint;
-    uptr RangesReleased;
+    uptr NumReleasesAttempted;
     uptr LastReleasedBytes;
     u64 LastReleaseAtNs;
   };
@@ -880,14 +880,14 @@ private:
           BytesInFreeList - Sci->ReleaseInfo.BytesInFreeListAtLastCheckpoint;
     }
     const uptr AvailableChunks = Sci->AllocatedUser / BlockSize;
-    Str->append("  %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
-                "inuse: %6zu avail: %6zu releases: %6zu last released: %6zuK "
-                "latest pushed bytes: %6zuK\n",
-                ClassId, getSizeByClassId(ClassId), Sci->AllocatedUser >> 10,
-                Sci->FreeListInfo.PoppedBlocks, Sci->FreeListInfo.PushedBlocks,
-                InUse, AvailableChunks, Sci->ReleaseInfo.RangesReleased,
-                Sci->ReleaseInfo.LastReleasedBytes >> 10,
-                PushedBytesDelta >> 10);
+    Str->append(
+        "  %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
+        "inuse: %6zu avail: %6zu releases attempted: %6zu last released: %6zuK "
+        "latest pushed bytes: %6zuK\n",
+        ClassId, getSizeByClassId(ClassId), Sci->AllocatedUser >> 10,
+        Sci->FreeListInfo.PoppedBlocks, Sci->FreeListInfo.PushedBlocks, InUse,
+        AvailableChunks, Sci->ReleaseInfo.NumReleasesAttempted,
+        Sci->ReleaseInfo.LastReleasedBytes >> 10, PushedBytesDelta >> 10);
   }
 
   void getSizeClassFragmentationInfo(SizeClassInfo *Sci, uptr ClassId,
@@ -972,6 +972,10 @@ private:
     const uptr Base = First * RegionSize;
     const uptr NumberOfRegions = Last - First + 1U;
 
+    // The following steps contribute to the majority time spent in page
+    // releasing thus we increment the counter here.
+    ++Sci->ReleaseInfo.NumReleasesAttempted;
+
     // ==================================================================== //
     // 2. Mark the free blocks and we can tell which pages are in-use by
     //    querying `PageReleaseContext`.
@@ -991,9 +995,8 @@ private:
     };
     releaseFreeMemoryToOS(Context, Recorder, SkipRegion);
 
-    if (Recorder.getReleasedRangesCount() > 0) {
+    if (Recorder.getReleasedBytes() > 0) {
       Sci->ReleaseInfo.BytesInFreeListAtLastCheckpoint = BytesInFreeList;
-      Sci->ReleaseInfo.RangesReleased += Recorder.getReleasedRangesCount();
       Sci->ReleaseInfo.LastReleasedBytes = Recorder.getReleasedBytes();
       TotalReleasedBytes += Sci->ReleaseInfo.LastReleasedBytes;
     }

compiler-rt/lib/scudo/standalone/primary64.h

@@ -530,7 +530,7 @@ private:
 
   struct ReleaseToOsInfo {
     uptr BytesInFreeListAtLastCheckpoint;
-    uptr RangesReleased;
+    uptr NumReleasesAttempted;
     uptr LastReleasedBytes;
     // The minimum size of pushed blocks to trigger page release.
     uptr TryReleaseThreshold;
@@ -1144,11 +1144,12 @@ private:
     Str->append(
         "%s %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
         "inuse: %6zu total: %6zu releases: %6zu last "
-        "released: %6zuK latest pushed bytes: %6zuK region: 0x%zx (0x%zx)\n",
+        "releases attempted: %6zuK latest pushed bytes: %6zuK region: 0x%zx "
+        "(0x%zx)\n",
         Region->Exhausted ? "E" : " ", ClassId, getSizeByClassId(ClassId),
         Region->MemMapInfo.MappedUser >> 10, Region->FreeListInfo.PoppedBlocks,
         Region->FreeListInfo.PushedBlocks, InUseBlocks, TotalChunks,
-        Region->ReleaseInfo.RangesReleased,
+        Region->ReleaseInfo.NumReleasesAttempted,
         Region->ReleaseInfo.LastReleasedBytes >> 10,
         RegionPushedBytesDelta >> 10, Region->RegionBeg,
         getRegionBaseByClassId(ClassId));
@@ -1322,7 +1323,7 @@ private:
                                             Context.getReleaseOffset());
     auto SkipRegion = [](UNUSED uptr RegionIndex) { return false; };
     releaseFreeMemoryToOS(Context, Recorder, SkipRegion);
-    if (Recorder.getReleasedRangesCount() > 0) {
+    if (Recorder.getReleasedBytes() > 0) {
       // This is the case that we didn't hit the release threshold but it has
       // been past a certain period of time. Thus we try to release some pages
       // and if it does release some additional pages, it's hint that we are
@@ -1342,7 +1343,6 @@ private:
       }
 
       Region->ReleaseInfo.BytesInFreeListAtLastCheckpoint = BytesInFreeList;
-      Region->ReleaseInfo.RangesReleased += Recorder.getReleasedRangesCount();
       Region->ReleaseInfo.LastReleasedBytes = Recorder.getReleasedBytes();
     }
     Region->ReleaseInfo.LastReleaseAtNs = getMonotonicTimeFast();

compiler-rt/lib/scudo/standalone/release.h

@@ -22,8 +22,6 @@ public:
   RegionReleaseRecorder(MemMapT *RegionMemMap, uptr Base, uptr Offset = 0)
       : RegionMemMap(RegionMemMap), Base(Base), Offset(Offset) {}
 
-  uptr getReleasedRangesCount() const { return ReleasedRangesCount; }
-
   uptr getReleasedBytes() const { return ReleasedBytes; }
 
   uptr getBase() const { return Base; }
@@ -33,12 +31,10 @@ public:
   void releasePageRangeToOS(uptr From, uptr To) {
     const uptr Size = To - From;
     RegionMemMap->releasePagesToOS(getBase() + Offset + From, Size);
-    ReleasedRangesCount++;
     ReleasedBytes += Size;
   }
 
 private:
-  uptr ReleasedRangesCount = 0;
   uptr ReleasedBytes = 0;
   MemMapT *RegionMemMap = nullptr;
   uptr Base = 0;
@@ -52,8 +48,6 @@ public:
   ReleaseRecorder(uptr Base, uptr Offset = 0, MapPlatformData *Data = nullptr)
       : Base(Base), Offset(Offset), Data(Data) {}
 
-  uptr getReleasedRangesCount() const { return ReleasedRangesCount; }
-
   uptr getReleasedBytes() const { return ReleasedBytes; }
 
   uptr getBase() const { return Base; }
@@ -62,12 +56,10 @@ public:
   void releasePageRangeToOS(uptr From, uptr To) {
     const uptr Size = To - From;
     releasePagesToOS(Base, From + Offset, Size, Data);
-    ReleasedRangesCount++;
     ReleasedBytes += Size;
   }
 
 private:
-  uptr ReleasedRangesCount = 0;
   uptr ReleasedBytes = 0;
   // The starting address to release. Note that we may want to combine (Base +
   // Offset) as a new Base. However, the Base is retrieved from