diff --git a/llvm/include/llvm/ProfileData/MemProf.h b/llvm/include/llvm/ProfileData/MemProf.h
--- a/llvm/include/llvm/ProfileData/MemProf.h
+++ b/llvm/include/llvm/ProfileData/MemProf.h
@@ -196,7 +196,7 @@
   };
 
   // The dynamic calling context for the allocation.
-  std::vector<Frame> CallStack;
+  llvm::SmallVector<Frame> CallStack;
   // The statistics obtained from the runtime for the allocation.
   PortableMemInfoBlock Info;
 
diff --git a/llvm/include/llvm/ProfileData/RawMemProfReader.h b/llvm/include/llvm/ProfileData/RawMemProfReader.h
--- a/llvm/include/llvm/ProfileData/RawMemProfReader.h
+++ b/llvm/include/llvm/ProfileData/RawMemProfReader.h
@@ -32,7 +32,7 @@
 
 // Map from id (recorded from sanitizer stack depot) to virtual addresses for
 // each program counter address in the callstack.
-using CallStackMap = llvm::DenseMap<uint64_t, llvm::SmallVector<uint64_t, 32>>;
+using CallStackMap = llvm::DenseMap<uint64_t, llvm::SmallVector<uint64_t>>;
 
 class RawMemProfReader {
 public:
@@ -75,7 +75,15 @@
                    llvm::MapVector<uint64_t, MemInfoBlock> &Prof,
                    CallStackMap &SM)
       : Symbolizer(std::move(Sym)), SegmentInfo(Seg.begin(), Seg.end()),
-        ProfileData(Prof), StackMap(SM) {}
+        ProfileData(Prof), StackMap(SM) {
+    // We don't call initialize here since there is no raw profile to read. The
+    // test should pass in the raw profile as structured data.
+
+    // If there is an error here then the mock symbolizer has not been
+    // initialized properly.
+    if (Error E = symbolizeStackFrames())
+      report_fatal_error(std::move(E));
+  }
 
 private:
   RawMemProfReader(std::unique_ptr<MemoryBuffer> DataBuffer,
@@ -83,6 +91,7 @@
       : DataBuffer(std::move(DataBuffer)), Binary(std::move(Bin)) {}
   Error initialize();
   Error readRawProfile();
+  Error symbolizeStackFrames();
 
   object::SectionedAddress getModuleOffset(uint64_t VirtualAddress);
   Error fillRecord(const uint64_t Id, const MemInfoBlock &MIB,
@@ -102,6 +111,10 @@
   llvm::MapVector<uint64_t, MemInfoBlock> ProfileData;
   CallStackMap StackMap;
 
+  // Cached symbolization from PC to Frame.
+  llvm::DenseMap<uint64_t, llvm::SmallVector<MemProfRecord::Frame>>
+      SymbolizedFrame;
+
   // Iterator to read from the ProfileData MapVector.
   llvm::MapVector<uint64_t, MemInfoBlock>::iterator Iter = ProfileData.end();
 };
diff --git a/llvm/lib/ProfileData/RawMemProfReader.cpp b/llvm/lib/ProfileData/RawMemProfReader.cpp
--- a/llvm/lib/ProfileData/RawMemProfReader.cpp
+++ b/llvm/lib/ProfileData/RawMemProfReader.cpp
@@ -132,7 +132,7 @@
     const uint64_t StackId = endian::readNext<uint64_t, little, unaligned>(Ptr);
     const uint64_t NumPCs = endian::readNext<uint64_t, little, unaligned>(Ptr);
 
-    SmallVector<uint64_t, 32> CallStack;
+    SmallVector<uint64_t> CallStack;
     for (uint64_t J = 0; J < NumPCs; J++) {
       CallStack.push_back(endian::readNext<uint64_t, little, unaligned>(Ptr));
     }
@@ -273,7 +273,46 @@
     return report(SOFOr.takeError(), FileName);
   Symbolizer = std::move(SOFOr.get());
 
-  return readRawProfile();
+  if (Error E = readRawProfile())
+    return E;
+
+  return symbolizeStackFrames();
+}
+
+Error RawMemProfReader::symbolizeStackFrames() {
+  // The specifier to use when symbolization is requested.
+  const DILineInfoSpecifier Specifier(
+      DILineInfoSpecifier::FileLineInfoKind::RawValue,
+      DILineInfoSpecifier::FunctionNameKind::LinkageName);
+
+  for (const auto &Entry : StackMap) {
+    for (const uint64_t VAddr : Entry.getSecond()) {
+      // Check if we have already symbolized and cached the result.
+      if (SymbolizedFrame.count(VAddr) > 0)
+        continue;
+
+      Expected<DIInliningInfo> DIOr = Symbolizer->symbolizeInlinedCode(
+          getModuleOffset(VAddr), Specifier, /*UseSymbolTable=*/false);
+      if (!DIOr)
+        return DIOr.takeError();
+      DIInliningInfo DI = DIOr.get();
+
+      for (size_t I = 0; I < DI.getNumberOfFrames(); I++) {
+        const auto &Frame = DI.getFrame(I);
+        SymbolizedFrame[VAddr].emplace_back(
+            // We use the function guid which we expect to be a uint64_t. At
+            // this time, it is the lower 64 bits of the md5 of the function
+            // name. Any suffix with .llvm. is trimmed since these are added by
+            // thinLTO global promotion. At the time the profile is consumed,
+            // these suffixes will not be present.
+            Function::getGUID(trimSuffix(Frame.FunctionName)),
+            Frame.Line - Frame.StartLine, Frame.Column,
+            // Only the first entry is not an inlined location.
+            I != 0);
+      }
+    }
+  }
+  return Error::success();
 }
 
 Error RawMemProfReader::readRawProfile() {
@@ -347,30 +386,10 @@
 Error RawMemProfReader::fillRecord(const uint64_t Id, const MemInfoBlock &MIB,
                                    MemProfRecord &Record) {
   auto &CallStack = StackMap[Id];
-  DILineInfoSpecifier Specifier(
-      DILineInfoSpecifier::FileLineInfoKind::RawValue,
-      DILineInfoSpecifier::FunctionNameKind::LinkageName);
   for (const uint64_t Address : CallStack) {
-    Expected<DIInliningInfo> DIOr = Symbolizer->symbolizeInlinedCode(
-        getModuleOffset(Address), Specifier, /*UseSymbolTable=*/false);
-
-    if (!DIOr)
-      return DIOr.takeError();
-    DIInliningInfo DI = DIOr.get();
-
-    for (size_t I = 0; I < DI.getNumberOfFrames(); I++) {
-      const auto &Frame = DI.getFrame(I);
-      Record.CallStack.emplace_back(
-          // We use the function guid which we expect to be a uint64_t. At this
-          // time, it is the lower 64 bits of the md5 of the function name. Any
-          // suffix with .llvm. is trimmed since these are added by thinLTO
-          // global promotion. At the time the profile is consumed, these
-          // suffixes will not be present.
-          Function::getGUID(trimSuffix(Frame.FunctionName)),
-          Frame.Line - Frame.StartLine, Frame.Column,
-          // Only the first entry is not an inlined location.
-          I != 0);
-    }
+    assert(SymbolizedFrame.count(Address) &&
+           "Address not found in symbolized frame cache.");
+    Record.CallStack.append(SymbolizedFrame[Address]);
   }
   Record.Info = PortableMemInfoBlock(MIB);
   return Error::success();
diff --git a/llvm/unittests/ProfileData/MemProfTest.cpp b/llvm/unittests/ProfileData/MemProfTest.cpp
--- a/llvm/unittests/ProfileData/MemProfTest.cpp
+++ b/llvm/unittests/ProfileData/MemProfTest.cpp
@@ -132,7 +132,7 @@
 
   EXPECT_CALL(*Symbolizer, symbolizeInlinedCode(SectionedAddress{0x2000},
                                                 specifier(), false))
-      .Times(2)
+      .Times(1) // Only once since we cache the result for future lookups.
       .WillRepeatedly(Return(makeInliningInfo({
           {"foo", 10, 5, 30},
           {"bar", 201, 150, 20},