diff --git a/llvm/tools/llvm-profgen/PerfReader.cpp b/llvm/tools/llvm-profgen/PerfReader.cpp
--- a/llvm/tools/llvm-profgen/PerfReader.cpp
+++ b/llvm/tools/llvm-profgen/PerfReader.cpp
@@ -1212,6 +1212,7 @@
   warnTruncatedStack();
   warnInvalidRange();
   generateUnsymbolizedProfile();
+  AggregatedSamples.clear();
 
   if (SkipSymbolization)
     writeUnsymbolizedProfile(OutputFilename);
diff --git a/llvm/tools/llvm-profgen/llvm-profgen.cpp b/llvm/tools/llvm-profgen/llvm-profgen.cpp
--- a/llvm/tools/llvm-profgen/llvm-profgen.cpp
+++ b/llvm/tools/llvm-profgen/llvm-profgen.cpp
@@ -158,6 +158,9 @@
       ProfileGeneratorBase::create(Binary.get(), Reader->getSampleCounters(),
                                    Reader->profileIsCSFlat());
   Generator->generateProfile();
+  // The Reader object, espcially its SampleCounters field, is not needed at
+  // this point, so releasing it to reduce peak memory usage.
+  Reader.reset();
   Generator->write();
 
   return EXIT_SUCCESS;