diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -96,9 +96,6 @@
 extern "C" int fileno_unlocked(void *stream);
 extern "C" int dirfd(void *dirp);
 #endif
-#if SANITIZER_GLIBC
-extern "C" int mallopt(int param, int value);
-#endif
 #if SANITIZER_NETBSD
 extern __sanitizer_FILE __sF[];
 #else
@@ -2668,12 +2665,6 @@
   REAL(memcpy) = internal_memcpy;
 #endif
 
-  // Instruct libc malloc to consume less memory.
-#if SANITIZER_GLIBC
-  mallopt(1, 0);  // M_MXFAST
-  mallopt(-3, 32*1024);  // M_MMAP_THRESHOLD
-#endif
-
   new(interceptor_ctx()) InterceptorContext();
 
   InitializeCommonInterceptors();