diff --git a/make/autoconf/flags-cflags.m4 b/make/autoconf/flags-cflags.m4
index 6298bcae416..1a6a040965b 100644
--- a/make/autoconf/flags-cflags.m4
+++ b/make/autoconf/flags-cflags.m4
@@ -93,8 +93,25 @@ AC_DEFUN([FLAGS_SETUP_DEBUG_SYMBOLS],
       )
     fi
 
-    CFLAGS_DEBUG_SYMBOLS="-g -gdwarf-4"
-    ASFLAGS_DEBUG_SYMBOLS="-g"
+    # Enough to produce viable backtrace without blowing up debug info size.
+    GCC_DEBUG_LEVEL=1
+
+    case $DEBUG_LEVEL in
+      slowdebug )
+        # Default to produce debuggable binaries
+        GCC_DEBUG_LEVEL=2
+        ;;
+    esac
+
+    UTIL_ARG_WITH(NAME: gcc-debug-level, TYPE: string,
+      DEFAULT: ${GCC_DEBUG_LEVEL},
+      RESULT: GCC_DEBUG_LEVEL,
+      DESC: [Sets the GCC debug level, when debug info generation is enabled],
+      DEFAULT_DESC: [from build debug level])
+    AC_SUBST(GCC_DEBUG_LEVEL)
+
+    CFLAGS_DEBUG_SYMBOLS="-gdwarf-4 -g${GCC_DEBUG_LEVEL}"
+    ASFLAGS_DEBUG_SYMBOLS="-g${GCC_DEBUG_LEVEL}"
   elif test "x$TOOLCHAIN_TYPE" = xclang; then
     if test "x$ALLOW_ABSOLUTE_PATHS_IN_OUTPUT" = "xfalse"; then
       # Check if compiler supports -fdebug-prefix-map. If so, use that to make
diff --git a/make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java b/make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java
index fe5938ce0e3..220face0868 100644
--- a/make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java
+++ b/make/langtools/src/classes/build/tools/symbolgenerator/CreateSymbols.java
@@ -282,6 +282,8 @@ public void createSymbols(String ctDescriptionFileExtra, String ctDescriptionFil
         try (OutputStream fos = new FileOutputStream(ctSymLocation);
              OutputStream bos = new BufferedOutputStream(fos);
              ZipOutputStream jos = new ZipOutputStream(bos)) {
+            // Do not compress ct.sym, allow external compressor to work on it.
+            jos.setLevel(0);
             for (Entry<String, Set<FileData>> e : directory2FileData.entrySet()) {
                 jos.putNextEntry(createZipEntry(e.getKey(), timestamp));
                 for (FileData fd : e.getValue()) {
diff --git a/src/hotspot/share/compiler/compiler_globals.hpp b/src/hotspot/share/compiler/compiler_globals.hpp
index 3919c596d74..fa5cd97c540 100644
--- a/src/hotspot/share/compiler/compiler_globals.hpp
+++ b/src/hotspot/share/compiler/compiler_globals.hpp
@@ -388,6 +388,11 @@
           "If compilation is stopped with an error, capture diagnostic "    \
           "information at the bailout point")                               \
                                                                             \
+  product(bool, InlineColdMethods, false, DIAGNOSTIC,                       \
+          "Inline cold methods that would otherwise be rejected based"      \
+          "on profile information. Only useful for compiler testing.")      \
+                                                                            \
+
 // end of COMPILER_FLAGS
 
 DECLARE_FLAGS(COMPILER_FLAGS)
diff --git a/src/hotspot/share/opto/bytecodeInfo.cpp b/src/hotspot/share/opto/bytecodeInfo.cpp
index 5b48b33aa46..98f5cb23990 100644
--- a/src/hotspot/share/opto/bytecodeInfo.cpp
+++ b/src/hotspot/share/opto/bytecodeInfo.cpp
@@ -295,6 +295,11 @@ bool InlineTree::should_not_inline(ciMethod* callee_method, ciMethod* caller_met
     return false;
   }
 
+  // accept cold methods if requested
+  if (InlineColdMethods) {
+    return false;
+  }
+
   // don't use counts with -Xcomp
   if (UseInterpreter) {
     if (!callee_method->has_compiled_code() &&
@@ -331,6 +336,9 @@ bool InlineTree::is_not_reached(ciMethod* callee_method, ciMethod* caller_method
   if (!UseInterpreter) {
     return false; // -Xcomp
   }
+  if (InlineColdMethods) {
+    return false; // CTW
+  }
   if (profile.count() > 0) {
     return false; // reachable according to profile
   }
diff --git a/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CtwRunner.java b/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CtwRunner.java
index 11694f72837..6a5d9d4e950 100644
--- a/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CtwRunner.java
+++ b/test/hotspot/jtreg/testlibrary/ctw/src/sun/hotspot/tools/ctw/CtwRunner.java
@@ -307,6 +307,8 @@ private String[] cmd(long classStart, long classStop) {
                 // Expand the optimization scope by disallowing most traps.
                 "-XX:PerMethodTrapLimit=0",
                 "-XX:PerMethodSpecTrapLimit=0",
+                // Artificially expand the scope of inlining in the absence of reasonable profile.
+                "-XX:+InlineColdMethods",
                 // Do not pay extra stack trace generation cost for normally thrown exceptions
                 "-XX:-StackTraceInThrowable",
                 "-XX:+IgnoreUnrecognizedVMOptions",