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8220388: Increase -inlinehint-threshold for Clang to avoid G1 pause time regression
authormanc
Fri, 08 Mar 2019 18:21:52 -0800
changeset 54646 5b1eec609909
parent 54645 05aaccf7d558
child 54647 c0d9bc9b4e1f
8220388: Increase -inlinehint-threshold for Clang to avoid G1 pause time regression Summary: Make Clang inline more aggressively for functions with inline keyword Reviewed-by: erikj, jiangli, shade
make/autoconf/flags-cflags.m4 file | annotate | diff | comparison | revisions 
--- a/make/autoconf/flags-cflags.m4	Mon Apr 29 16:01:52 2019 -0400
+++ b/make/autoconf/flags-cflags.m4	Fri Mar 08 18:21:52 2019 -0800
@@ -536,6 +536,12 @@
     TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM -mno-omit-leaf-frame-pointer -mstack-alignment=16"
 
     if test "x$OPENJDK_TARGET_OS" = xlinux; then
+      if test "x$DEBUG_LEVEL" = xrelease; then
+        # Clang does not inline as much as GCC does for functions with "inline" keyword by default.
+        # This causes noticeable slowdown in pause time for G1, and possibly in other areas.
+        # Increasing the inline hint threshold avoids the slowdown for Clang-built JVM.
+        TOOLCHAIN_CFLAGS_JVM="$TOOLCHAIN_CFLAGS_JVM -mllvm -inlinehint-threshold=100000"
+      fi
       TOOLCHAIN_CFLAGS_JDK="-pipe"
       TOOLCHAIN_CFLAGS_JDK_CONLY="-fno-strict-aliasing" # technically NOT for CXX
     fi
jdk-sandbox