[compiler-rt] [scudo] Add fragmentation info for each memory group (PR #107475)

[Christopher Ferris via llvm-commits]

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@@ -1193,6 +1205,51 @@ template <typename Config> class SizeClassAllocator64 {
                 AllocatedPagesCount, InUseBytes >> 10, Integral, Fractional);
   }
 
+  void getMemoryGroupFragmentationInfoInRegion(RegionInfo *Region, uptr ClassId,
+                                               ScopedString *Str)
+      REQUIRES(Region->MMLock) {
+    const uptr BlockSize = getSizeByClassId(ClassId);
+    const uptr AllocatedUserEnd =
+        Region->MemMapInfo.AllocatedUser + Region->RegionBeg;
+
+    SinglyLinkedList<BatchGroupT> GroupsToRelease;
+    {
+      ScopedLock L(Region->FLLock);
+      GroupsToRelease = Region->FreeListInfo.BlockList;
+      Region->FreeListInfo.BlockList.clear();
+    }
+
+    constexpr uptr GroupSize = (1UL << GroupSizeLog);
+    constexpr uptr MaxNumGroups = RegionSize / GroupSize;
+
+    MemoryGroupFragmentationRecorder<GroupSize, MaxNumGroups> Recorder;
+    if (!GroupsToRelease.empty()) {
+      PageReleaseContext Context =
+          markFreeBlocks(Region, BlockSize, AllocatedUserEnd,
+                         getCompactPtrBaseByClassId(ClassId), GroupsToRelease);
+      auto SkipRegion = [](UNUSED uptr RegionIndex) { return false; };
+      releaseFreeMemoryToOS(Context, Recorder, SkipRegion);
+
+      mergeGroupsToReleaseBack(Region, GroupsToRelease);
+    }
+
+    Str->append("MemoryGroupFragmentationInfo in Region %zu (%zu)\n", ClassId,
+                BlockSize);
+
+    const uptr MaxNumGroupsInUse =
+        roundUp(Region->MemMapInfo.AllocatedUser, GroupSize) / GroupSize;
+    for (uptr I = 0; I < MaxNumGroupsInUse; ++I) {
+
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cferris1000 wrote:

Super small nit, I think you can delete this blank line.

https://github.com/llvm/llvm-project/pull/107475